One answer to your question is that a girl could be a "tom-boy" whenever she wanted to be. Then she could switch back to being a girl whenever she wanted to be that. It is/was nearly impossible for a boy to sometimes be like a girl and sometimes be like a boy. Society frowns at this; sometimes withe dire consequences.
Also, there is nothing particularily interesting about male clothes. While women's clothes are quite fascinating as well as being pretty and feeling good to the touch! So, there is not much incentive for a female to crossdress.
