Tesla's vision is full self driving.

You do need a certain amount of balance, even at speed, if you've ever ridden a motorcycle or a bicycle even, you'll realize that shifting your bodyweight is a way of adding additional steering. If you fell asleep on a bicycle or motorcycle, you would fall. Tesla is trying to remove human error with FSD, and this is very much a human error thing

Also, even with autopilot, vehicles still need to stop at stop signs, stop lights (these could mainly be removed if every vehicle was in communication and they added another way for pedestrians to cross motorways without crossing the actual road making vehicles stop, but we're getting deep into the future here). Motorcycles are a luxury driving experience, people don't really ride them because they're particularly ideal. People riding a motorcycle specifically wouldn't want autopilot :)

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So it makes sense that Tesla is only interested in building leisure hobby EV toys