Perhaps it's not merely about easy/difficult, but there are other factors as well? Consider that for a moment? I think physics is very formalized, very sterile

Perhaps it's not merely about easy/difficult, but there are other factors as well? Consider that for a moment? I think physics is very formalized, very sterile, and very rigid. It is often theoretical and abstract (if you're taking classes on it, anyway). I think that these features don't readily appeal to conventional girls. I think girls enjoy things that are immersive, and highly visual/audible, for example ballet, or art, or theatre. Now my mother has a degree in English literature, and I can see that being a girl thing too, as it is highly verbal and immersive, though not so visual/audible, and literature lets you read great women authors and then gives you the chance to write your own stuff, too. In physics, you can study great engineering and rockets and lasers and stuff, but as for making your own stuff, you're pretty much limited to baking-soda volcanos and water rockets, you know? Let's not also forget the pre-existing status of physics as a male-dominated field. So if you have male physics teachers and male physicists to study and male-written textbooks and most of your Physics classmates and majors are male, well, I would say that girls don't enjoy being that kind of minority, unless they are activists, and neither do boys enjoy being in a girl-dominated milieu.