Bad weather can develop around you, and when flying you can't just pull over and wait for it to pass. A cliff doesn't suddenly develop in front of your minivan.

Bad weather can develop around you, and when flying you can't just pull over and wait for it to pass. A cliff doesn't suddenly develop in front of your minivan. A relatively minor error can quickly develop into a situation well beyond your control, without any way out of it. That kind of fatal escalation is pretty much impossible with road vehicles.