That 360 degree visibility only applies one way, the other drivers won't see you.

When you are on two wheels, you are practically invisible. Drivers can look you straight in the eyes and still cut you off and make turns right in front of you. I say this as somebody who frequently rides both bicycles and motorcycles on roads.

For many people it's just not worth the risk. Of course, better infrastructure would help with this problem, but good luck with that.

Belt and shaft driven bicycles do exist. You just wouldn't want to ride one, the loss of efficiency over chain requires you to make up for it with your legs and that is not fun.

Enclosed chain bicycles are kind of a reasonable trade-off.

This is what I am really waiting for, to be honest. Jerboa is too slow and jerky for my liking.