As others have mentioned, public transit beats uber/lyft when its actually the better, faster service (e.g. London, Tokyo).
But when public transit is poorly planned, slow, dirty, crime-ridden like it often is in the US, uber/lyft wins every time. Even when cities like San Francisco choose to spend billions on improving public transit, they mess it up every single time. There's a long list of hilariously short sighted decisions made on projects like the Transbay Terminal, The Central Subway, Geary/Van Ness BRT.
My daily commute literally runs along the t-line in San Francisco, but I never take it because it's basically the same speed as walking, slower than biking, slower than uber'ing. Poor planning and management is the cause of public transit's decline.
SF needs to significantly invest in transit with dedicated rights of ways, preferably along more important routes than the Central Subway. And if subways are too expensive or difficult to build, we need to seriously consider using elevated light rail instead. Geary road, for example, would be perfect for an el.
Uber and Lyft have not been the best actors, but someone was going to step in and profit off of public transit's incompetence here.
Even prior to the prevalence of rideshares, Boston was dealing with absurd corruption in attempting to expand on the public transit systems. See: Green Line Extension project
Of course when a substitute improves, some people will switch. However, the root cause is the declining quality and lack of improvements to the system that even gives a substitute the chance to compete.
I honestly don't understand how 100 years ago nyc was able to build an expansive subway system and today it takes decades to add a new station. I know it's a combination of land costs, labor costs, corruption, regulation, underground congestion (and that the original lines were built by private companies) but I still don't really understand the situation.
A quick search turned up this piece on 16 deaths around 1904 during construction of a NYC subway line. There are famous pictures such as this one of construction of high rises in New York without any safety equipment whatsoever. But it was built in 14 months! All that safety gear is expensive and slows down construction. In climbing, we often joke 'no belay, no delay', because of how fast you can climb when you don't take the time to fix your ropes, etc. 
I've been riding the T in Boston for the better part of 20 years now. My usage of rideshares is more related to convenience and timing than any change in MBTA service. A lot of trips I do require going into/out of the core city to make a lateral move, or to coordinate multiple modes with different headways, e.g. 5 minutes for subway, 10 minutes for one bus, 25 for the next. The result is that time in motion is similar to the rideshare, but I spend an equal amount of time waiting for a connection.
I'd really be curious to see the effect on trips that already have a direct or reasonably efficient multi-step itinerary, e.g. Davis to Charles/MGH, Sullivan to Harvard, etc.
People just want to take the path of least resistance and there's a lot of young tech workers with low expenses and high salaries who don't think about the long-term impact of the money they're spending on unnecessary conveniences instead of saving.
The real problem is that complaints about a shard public resource grow disproportionately like a meme and people codify that public transportation is terrible and unreliable, when in reality it's imperfect and that's an exaggeration.
I just hate Uber Pool and Lyft Line - the routes they take are often side streets with lots of congestion and turns, there's a lot of frustration when you're almost to your destination or to a major road and then the driver turns around to pick up another passenger. Drivers often play music I find annoying.
When I'm in Tokyo I don't use Uber because the train system is so clean, fast, and safe; I have no incentive to use an Uber.
When I'm in places with slow buses that get stuck in traffic, or operate trains with disgusting facilities, I'm more likely to choose Uber.
Exactly. Improve the quality of public transportation and the usage levels of Uber and Lyft will decline. Whatever the failings of Uber and Lyft, and there are many, they can't be used as a justification to curb their use (essentially eliminate competition) so public transportation systems can continue their unchallenged mediocrity.
When the wealthy are forced to use public services, all of a sudden, they become interested and politically engaged in improving them.
Uber doesn't drive improvements in transit in this sense - it starves it of political capital.
The best transit services are ones which are used by a wide swathe of the public.
 If you are regularly paying $6-30 for a one-way taxi commute, you are either wealthy, really money-foolish, or a truly special case.
Costs me $0/day to take the bus or light rail, subsidized by my workplace. $3-$4 if your workplace doesn't subsidize and you get a regional pass.
Ride-hailing services don't have this particular problem. They only need to serve based on rider demand. Yet at this moment they do rely on subsidies by VC money.
Take the DC metro for example - it used to be arguably the best public rail system in the country. Now, through mismanagement and neglect, it's pretty awful. IMO dirty, unreliable public transport created a massive void that Lyft/Uber have filled.
The Muni bus would have taken 31 minutes according to Google Maps (with much higher expected variance, based on my personal experience) and would have cost $2.50 (or $2.75 if I didn’t have a preloaded Clipper card).
Because of that expected duration variance; the probability of sharing a bus or bus stop with a profoundly troubled, violent, or dirty person; and the fact that the difference between $2.50 and $14 is not very significant to me; taking a Lyft was an extremely easy decision for me.
If public transportation was better, I wouldn't use Lyft as much as I do these days.
It'd be interesting to look at countries known for their exceptional public transportation and see if they saw a decline when Uber and Lyft came on the market.
>“Perhaps the presence of innovative modes makes it a more compelling or sexier question to ask, but I think there are lots of reasons people aren’t taking these modes as much as before,” said Susan Shaheen, the co-director of the Transportation Sustainability Research Center at UC Berkeley and an expert in shared mobility. “The question of causality is perplexing and hard, and it’s not necessarily one thing.”
So basically, shocker, correlation does not equal causation and there's a lot going on driving this change.
Also, it'd be interesting to see data that took into account different modes. Light rail ridership in the Twin Cities has soared because (unlike our bus system) it is reliable and predictable, plus easier to use multimodally etc. etc.
And I imagine that most places share the Twin Cities' struggles to combat lawmakers in greater MN who have decided that investing in metro transit is a certain evil.
But that gets complicated when we're talking about second-order effects. To second order, yes, it does matter. I have taken both the bus and a Lyft to work when my car was inaccessible. There is competition there, and it's driven by bus transfers. To get close enough that I do not have significant walking to do, I have to accept delays due to bus transfers, and the weather has to be nice enough that I can easily endure those waits outside. Or my budget needs to be tight enough that that makes sense.
It's not surprising to me that public transit sees somewhere in the range of 5-20% decline due to the cheaper taxi service; that is about the range of those second-order effects. But this is also an avoidable loss: with the widespread use of cell phones it may be possible that routes become more customizable, not unlike how school buses work: "this route serves to bring people from that general area to this general area, but of course we tailor it a bit to the individual student population, we don't go down any side-streets if there are no students to pick up there." There is a great potential when city institutions start to get the hang of this new technology stuff, that a bus service could meaningfully get you from where you're at to where you're going without any big pain points, on the assumption that you have a smart-enough cell phone. And that's no longer the marker of wealth that it used to be. If they can really get it right, they can even have the ride-hailing services tied into those systems, the way that cab lines informally used to be: "we're willing to send a fare your way for someone starting at hub X and going to location Y which is outside of our service regions."
So it's possible with some transfers etc., it's just sufficiently inconvenient and slow that I've ruled that out.
I have a CTA pass so I almost never use Uber/Lyft because it's so much more expensive.
what people in this thread seem to be forgetting is that a lot of people don't actually have money to choose the service according to which is better - they take what they can afford, which is public trans. when rich people don't need to take the same forms of transit, then theres less pressure by the powerful people in society to create change, to improve the system. in the long run, we would all benefit directly, and indirectly (the positive effects it has on society), from a robust, affordable, pleasant, clean, etc public transit system. but because of this stratification, which uber/lyft contribute to (but of course cant be held entirely responsible for), it never gathers the clout and momentum to actually happen.
I know it's more complicated than it seems, but check out Tokyo. Their public transit works incredibly well, and a lot of public resources are spent making sure it stays that way. Some of this is due to the fact that Tokyo is an extremely new city in terms of a lot of its infrastructure (due to WW2), but that's not the whole story here.