Looking at most of the folks that do it, it seems like it's more about being different. You can get used to just about anything but I mean you spend the vast majority of your time driving and navigating the vehicle moving forward. It's just easier and more natural and then when you do have to back out you're backing out into a larger and normally less obstructed space. When ICE vehicles do it on rare occasion they kill some plants and on even more rare occasions start fires.
I got used to back-in parking in my ICE SUV days. I found it easier to park a 4-wheel drive vehicle back-in than front-in. And definitely safer when leaving the spot since the back of the vehicle was so long. And that was before rear cameras were a thing. With the hi-res camera, huge screen, and the lines, back-in parking is a breeze in my S.