Compare: Jaguar "designed sound" with a U.S. Army M1A2 turbine powered tank starting up.
(I once considered using that sound as a boot-up sound, but decided it would get annoying after a while.)
The pedestrian safety argument makes some sense, but I can't help wondering if there could be a better way than to add to the noise pollution.
In fact, that would be a hell of a business prospect - custom ship sounds for your whip. That alone would convince me to go electric.
Except for that one guy who's car would make a screaming sound as it passes by.
Which has a different tone than the "let's just not bother" vibe I get from the original version.
There's been research going on for at least the last 10 years into both the risk and effective sounds that don't simply prove annoying (like a beep would), or lose directionality.
My Volt makes a somewhat annoying tone below 25 mph, but I'm glad it does because almost immediately after getting it I noticed an increase in close-calls in parking lots when pedestrians would walk into the path of the car.
The noise isn't too car-like so it's less effective than the engine noise people are used too, but it's also probably more effective than nothing.
Given that there is increased lack of "looking while you walk" from many people (due in part to the use of smartphones) noise from vehicles becomes a crucial indicator.
Also, anybody else finds it funny the self-fulfilling prophecy where we're now actually projecting "hums" and "whooshes" on the outside of our cars that sound like what, in our minds, is what "future vehicles" should sound like?
And can we have 3rd party sounds? I'll make mine constantly say the "Move it, move it!" from Police Academy . It'll be fine.
The Jag's sound effect is cool, but there'll always be a nagging thought that it's an empty embellishment, like those aftermarket turbo valve sound emulators and blue-tinted pseudo-xenons so popular in certain... erm... modding circles.
VW calls the system Soundaktor, as another example. You'll see it implemented one of a few ways (or a combination): fake sound being piped through the speakers, real sound being piped through the speakers, a physical breach in the engine firewall to allow sound through, additional speakers in the firewall-area specially tuned for engine noises... etc.
They're very common. Startlingly common. I'd bet that you, the person reading this, has one in your car and you don't even know it.
Turbo'd engines inherently produce fun sounds and (most) manufactures silence them with overly restrictive intakes and exhausts. Why fake it when they can actually make it?
 2017 Mercedes CLA250
 Ford Mustang, F-150
 Porsche, Lexus LFA
The list goes on. Ford and VW are the worst, but every ICE auto manufacturer does it to some degree.
There's nothing funnier than hearing someone act so smug with the sound of revving their A3 2.0T, then telling them to get out of the car and listen to it from the outside, watching the look on their face when they realize it sounds like a V6 on the inside and a lawnmower on the outside.
Basically, if your car has a turbo'd 4 cyl engine made recently, you almost definitely have fake engine noise. As displacement goes up, the need for it goes down, but even the most popular V8 engines have it (everything Ford makes, Audi does it as well). The only manufacturer in this class that I can't find any evidence deploying fake engine noise is Mazda, but given their close relationship with Ford it wouldn't surprise me.
I remember reading about how the Mazda Miata was tuned to have a nice exhaust note when it first came out, but that isn't what I would call fake engine noise. Conducting sound where and how desired doesn't make it fake.
I also note some of your citations appear to involve random and possibly confused people making guesses on enthusiast forums which are less than an authoritative source.
I mean, this just sounds super annoying : https://youtu.be/vuhPZTrSmBw?t=20
I can see engine noise design becoming a thing. Reminds me of that old game "Full Throttle". To make the engine noise there they sampled a lion roar, a bengal tiger, and a jet engine: https://youtu.be/rf9xqsmO9m4?t=107
I don't buy the safety argument either really, additionally it's incredibly wasteful. Part of the issue with ICE engines was that they were constantly trying to reduce engine noise because if it's making too much noise/heat then that's energy that's being wasted in transfer. Now we're emulating that?
I considered motorcycle engines to be excessive too, but people always defended the ear-deafening sound as being "for safety" (when really, they just liked making noise and having the vibrations rumble through their bodies)
Only at slow speeds, up to 19mph. Above that, the external noisemaker is supposed to turn off. It's so pedestrians will notice a car making a turn through a crosswalk.
There's a guy who would know a lot about sci-fi spaceship sounds.
Thanks for the link!
Along the way he picked up Johnny Smith as a co-host, who is a more traditional "car geek", though also hugely exuberant for electric cars, by first interviewing Johnny for his Flux Capacitor project  (Johnny rebuilt a classic Enfield British electric car with modern electric car parts). Between the two of them Fully Charged has definitely become one of the most interesting and informative electric car shows in the world.
Sure, easy thresholding on speedometer data. Gimme a few hours.
> ... and check if there are pedestrians closer than a certain distance
I'll need a research team and five years. 
These Chinese market electric cars are not as fancy inside as your plush Jaguar or Tesla, they have bits of hard plastic everywhere rather than an exuberance of leather (or 'vegan leather'). The people that buy these cars really like them as the comfort comes from the silence, not the novelty cup holders/infotainment systems and other nonsense that motorists in the West think they need these days.
They still have to sit in gridlock and they still have to give up a lot of their day to the demands of the commute. From the glimpse into the future afforded by what is going on in China I suspect that these fake car noise things are not what the customer really wants. Tranquillity is much nicer than gimmickry. It is as simple as that. Might as well get some work done if you are a passenger in one of these cars or enjoy some quality time with your social media apps on your phone. There is no need to get your inner nine year old out, the cheap thrills of spaceship noises get boring if listened to every day, the novelty wears off.
The other thing is that these affordable electric cars will be coming here soon. Complete with hard plastic interiors. Imaginably there will be Trump taxes and tariffs that make these cars expensive compared to a 'Chicken Tax' SUV/truck, however, if there was to be free trade then these cars will be half the price of these up-market Jaguar things. They might not have the 'ludicrous mode' but who needs that if you are inching through bumper-to-bumper rush hour traffic?
These affordable EVs might not have fake whooshing noises inside the cab, so the question then becomes one of would you really want to pay for that? Why would anyone pay $$$ for these funny noises that a cheap toy designed for a nine year old could make?
Note that EU and other mandated exterior noises are for outside the passenger compartment, not for in it.
If you had one of these cars and you could download an app that used your phones sensors to play fake whooshing noises to make up for the absence of in-built fakery, would you bother?
I suspect that within a generation or two people will reject the noise of the internal combustion engine, even if V12 and turbocharged. It will be as anachronistic as wanting to hear horse hoof clatter and the whip of a buggy whip. But we are not there yet, hence the fakery.