Oh I hate this. I agree with Mollycuddles, it is, at least in part driven by the money making drive to sell parents two of everything, and generally make handing stuff down harder.
But it must also be driven by what sells (I.e. What parents want..)which companies are responding to. ELC started off all wood-and-primary-colours with earnest educational toys, but in the end went down the princesses or diggers route.
I hadn't thought about in terms of supernatural versus constructed, Milly but that is exactly right.
It used to be that where there were boys toys they were imitations of dad and prepartion to follow stereotypically male roles --, driving and fixing the car, doing woodwork around the house, understanding the world in scientific terms and doing engineering/ manufacturing job etc and girls toys were imitations of mum - the toy ironing board, dolls, and of the limited range of aspirations for women - nurse, teacher or glamerous wife to Ken.
Now its like we don't want to push girls into toys that are just about domesticity, so parents and toy companies are casting around for powerful role models for girls and the only ones they could come up with for the mass market was the power of woo and sexuality. It's profoundly depressing.
As for books, am I wrong in thinking that all pink/sparkly/princessy books and most spy/monster/adventure books of the kind you get in supermarkets are just rubbish, kind of junk food of children's literature?