Consider that not all malfunctions of a car leads it to crashing into things. The fuel system, the engine, the transmission and even the steering can completely break down and the car will still came to a stop. They are equipped with redundant brakes, and are always supported by the ground.

At the same time an aircraft is much more precarious. If anything in the fuel, engine, transmission, props, or control surfaces go wrong it will come down and fast. They have much more potential energy than a car (because they are high up). They also typically have much more kinetic energy because they have to move faster to maintain lift if they are fixed winged, or they have to have fast rotating parts if they are rotary winged.