The basic design of roads and their surroundings mean that an out-of-control car is relatively unlikely to collide with a building, as opposed to another car, a

The basic design of roads and their surroundings mean that an out-of-control car is relatively unlikely to collide with a building, as opposed to another car, a utility pole, a divider/barrier, etc. Conversely, an aircraft falling over a built-up area is very likely to encounter a building, and even if it lands in a road, it's going to be harder for moving cars to spot and avoid than an out-of-control car would be.