Safety, risk of losing lives, is a factor missing from the constraints imposed on PC manufacturers. Safety may play a larger role as an obstacle on this idea getting real traction.
I've seen a good amount of destroyed audio equipment resulting from the owner failing to do compatibility research beyond verifying that two components could be connected together. "What's an ohm? Do I need one of those?"
I've seen people get the most baffled faces from not being able to pass a high bandwidth signal through the hundreds of feet of hilariously thin uncertified HDMI cable that they just ran through their walls. "But the box said high speed!"
Interchangeable batteries in cars would mean that drivers are only one el cheapo Amazon third party generic out-of-spec "compatible" battery away from stopping at a red light next to a moving bomb.
When I read "interchangeable batteries" I imagine a pretty simple procedure: open hatch, pop out old battery, put in new battery, close hatch.
When I read "install car parts" I imagine a procedure at least an order of magnitude more difficult requiring knowledge and experience working on automobiles.
Changing batteries is a task nearly all people have done at least once by the time they start driving. If changing the batteries in your car is as easy as changing the AAs in your Game Boy then I imagine many people would be willing to do it without thinking twice.
I mean, you know, it's not the same size and doesn't serve the same purpose, but today people's cars have batteries in them and you can walk into Sears and buy one. I assume the battery for an EV is huge and not conveniently located though.
I spent a year in Japan and the contrast between Japan in the US as far as the average age/condition of cars you see on the road is quite striking.