Why are child safety seats required in cars but not in the airoplane

The easiest answer would be that in the aeroplane is to small space, and if just six person will have with them a special safety seat for their child, there probably would be to tightly. When you travel by your car, you have to concentrate on your drive, so child have to be in special seats, opposite to

an aeroplane when during the fly, suddenly can start the turbulence. But in this situation parents are near their kids, so they would be able to hold them, for they safety.