Because it is a legal question, not a technological one.
Now, I don’t know if the for example US traffic law has a tickbox somewhere a manufacturer can go and mark that they will take full responsibility in case of any accident and it will never be the result or liability of the owner/“driver” of the car, but until it does exist there is only supervised self driving, no matter how well or poorly it actually functions or what it does.
Even the current robotaxi endeavours are just one major fatal accident away from grinding to a halt when the courts start figuring out who in the chain from insurer to owner to manufacturer and every worker and designer who has even remotely touched the project is actually responsible for that death.
Emulation and emulators aren’t illegal. Yuzu for example got in trouble mostly for distributing tools for circumventing copy protection and dumping roms and not for the emulator itself.
But it doesn’t really matter as nobody has money to defend themselves against something like Nintendo. Here just even the threat of it was enough to get the Ryujinx devs to fold just in case.