Those phones were lasting for a week on single charge but novadays phones are hungry, many people carry external power banks or whatever they call them these days. I would happily use swappable battery. Design could also be improved so you can quickly slide empty battery out and charged one back in. Phones could have tiny built in battery which would make the process without the need to turn off/on the phone.
As someone who seems to be a vocal advocate for swappable batteries, I've got a genuine honest question to ask. What's significantly better about a swappable battery vs. an appropriately sized for your needs USB battery pack?
One big benefit is being able to replace the battery after the capacity is reduced due to age. If you get a new phone every couple years anyway this is probably less of a concern, but it's rather nice to be able to spend tens of dollars to get 100% capacity again vs hundreds of dollars for a new phone (even if it's a bit faster).
Even the new iPhone 7 (picking it as Apple is potentially the worst at user friendliness re: batteries) can have its battery replaced fairly easily if its aging. Yes, it's not as simple as popping a latch and snapping in a new one, but it's still very achievable and for a reasonable price (unless you go to Apple that is).
Having a replaceable battery has easily extended the life of my Samsung Galaxy S3, which has lost the ability to charge through the micro USB port (from what I understand this is a fairly common problem).
There are certainly other ways to fix this issue (ranging from switching to inductive charging to, if your good with soldering, actually swapping out the micro USB port on the board). But swapping out a battery is so simple, even not very technically inclined people can do it.
I'm not sure I could say the same for something like a iPhone 7 battery swap (such as this -- https://www.ifixit.com/Guide/iPhone+7+Battery+Replacement/67... ) -- I agree it looks doable, but non-technically inclined people might run away from those type of instructions.
There are numerous places across the globe that will do the work cheaply, usually for about the price you'd pay for an extra battery for the few modern phones that allow you to swap batteries still.
The problem with USB battery packs is that the connector is fragile and awkward. You can't really use the phone when you're walking around while the external battery is connected.
I have a spare battery for my phone and it's very convenient. Swap the battery and you're back to having a 100% charged fully usable device in about 30 seconds.
What kind of battery pack are you talking about. I fairly regularly have my battery in my jacket pocket and easily can use my phone, including making calls if needed, while plugged into the battery via a standard USB cable.
You can swap-and-go with charged phone in seconds. You leave empty battery for charging - you don't carry anything you don't need to think about your phone and battery pack charge level.
Wearing gloves reduces the usability of a phone too. Thankfully people find a solution rather than ranting on the Internet about things that are easily solvable. YMMV! :)
The Moto Z family has something similar (an internal battery plus an optional removable external battery). And from what I've read, the technology it uses seems to be in part based on Google's modular phone prototype.
