Exactly. Children have decent hand-eye coordination as toddlers. By 3 or 4, they can drive toy cars; by 5 they're riding bikes. But it takes them another decade or more to have the knowledge and judgment needed to drive a car in traffic. And even then they're not great; teens have a crash rate something like 3x other drivers.

Because of immaturity, not cognitive or physical capability. Kids start racing go karts as young as five - and that's a far more difficult, requiring fast reflexes, precise car control, and situational awareness. It's a far more challenging task than an average commute.

Not really, racing carts is primarily about the ability to control the thing under very well defined conditions (read: much better than your average 3 lane highway with hundreds of other road users) with other road users with the exact same end goal.

Exactly. "Immaturity" includes a big lack of detailed domain knowledge and domain-specific judgment, which is one of the things I think is going to be very hard to teach to computers.

I think domain specific judgement is what computers excel than human.

What human has advantage of is utilizing knowledge in unrelated domain to another domain.

Depends on what you mean by "domain", I suppose. But driving is a very broad domain. One has to understand human custom, human psychology, and human ethics, for example. As well as the behavior of wildlife, some applied meteorology, and a fair bit of understanding of both law and police practice. To a computer, these might be unrelated domains, but they aren't if you put a computer behind the wheel.