Level 5 means "people inside are purely passengers and never have to take steering wheel". For humans, being level 4 means that because of some road condition, driver gets out of the car and asks someone else to drive - either one of the passengers, or some sort of emergency 3rd party service.

I never did this myself (except while learning how to drive). And I don't think I've heard about my friends doing this either. Turn around because the road was impassable? Sure. Pass the wheel to someone else? nope.

That means a lot (most?) human drivers are "level 5 autonomous".

I do pass the wheel over on long trips. We take turns and we swap when someone feels to tired to remain sharp.