It's rooted in the sexist idea that women are not capable of making decisions about their sexuality.

There's a weird double standard around "love is love" for women. No one is concerned if an adult male has sex with a substantially older partner or engages in sex work, but if a young (adult) woman dates an older man or decides she wants to be a sex worker it's considered fraught.

This is a relic of the patriarchal order that many feminists still cling to.