A、Because boys and girls are being prepared for different social roles. B、Because boys are more courageous. C、Because toy makers

There seems never to have been a civilization without toys, but when and how they developed is unknown. They probably came about just to give children something to do.
  In the ancient world, as today, most boys played with some kinds of toys and most girls with some other. In societies where social roles are rigidly determined, boys pattern their play after the activities of their fathers and girls after the tasks of their mothers. This is true because boys and girls are being prepared, even in play, to step into the roles and responsibilities of the adult world.
  What is remarkable about the history of toys is not so much how they changed over the centuries but how much they have remained the same. The changes have been mostly in terms of craftsmanship, mechanics, and technology. It is the universality of toys with regard to their development in all part of the world and their persistence to the present that is amazing. In Egypt, America, China, Japan, and even among the Arctic peoples, generally the same kinds of toys appeared. Variations depended on local customs and ways of life because toys imitate their surroundings. Nearly every civilization had dolls, little weapons, toy soldiers, tiny animals and vehicles.