Also, it should be noted that in Go, we're trying to beat the BEST human player, and have done so. In driving, we're just trying to be "good enough" or safe enough -- it doesn't have to be the safest driver in the world.

Beating the average human Go player was probably accomplished decades ago, whereas it's not even clear if we're safer than the average human driver (under all conditions).

These tasks are just wildly different, and yes I think it's basically all due to the fact that Go's state is so easily represented by a computer, and the goal is so concrete.