The 3DS screen kinda sucked though. It only worked well when your eyes were inside a very tight cone straight in front of the screen. Move your head just a little bit and the image went to shit. And even when it did work, it looked more cool than good, if that makes sense. That narrow fov thing is an inherent limitation of the technology that can hardly be worked around, and it makes it practically useless for TVs. Multiple people can’t view that screen because you can’t expect everyone to be in the vision cone at once. You can’t even properly view it alone because you won’t be staying inside that narrow vision cone the whole time you’ll be sitting on your couch watching Avatar.
I never saw mine as anything more than a cool gimmick, and kept its 3D-ness turned off 95% of the time. There’s a reason Nintendo didn’t pursue it further.
Because for phones they kinda are custom. The smartphone hardware landscape is an absolute clusterfuck of proprietary blobs and closed source drivers and all sorts of shit that makes it so you need a lot of work to customize the base os to work on any particular device. ROMs have rather short lists of compatible phones, and each one of those had to have a build specifically developed for them. You can’t take, say, grapheneos and slap it on any phone you like.