I like some of the sub forums in non-hair. I don't know too much about recipies and books, but the others, I see a good reason to keep.
Politics is to keep fighting down. Parenting is nice because you're more likely get a response from from other parents. I like fitness and make-up because non-hair is busy and topics can get quickly buried and forgotten, so you get more time on the first page. The smaller forums make it easier to search. Since most of the topics are on products, necro'ing a old thread doesn't feel weird unless they're trying to advice the OP who asked a question 5 years ago. And threads don't get derailed as much, if any. I don't mind derails, but it's nice to have a place to ask about let's say lipstick without it being turned into a conversation about uncrustables.
I've always thought it would be cool if there was a fitness swap where you could trade videos with others.