Why do marble statues have no arms?

Very old statues usually get a lot of rough handling and they break off. The old classic look of statues with broken arms has become a sort of symbol for classic art and so is often recreated in more recent statues. But the originals did have arms! A lot of people like the esthetic look of the broken arms and consider the form of the bust or torso to be the perfect body form, and arms become a distraction to them.