There are threads here about how women sleep with hot guys in hopes of getting them, but they cannot manage to lock them down because the hot guys want to sleep around and have casual sex.

However, as a guy, I have had a couple of experiences with women over the years where they wanted a casual sex f-buddy and I developed feelings for both of them and wanted to take things further, and they refused, saying they just want casual only.

I am wondering, what is the female motivations most likely for just wanting casual only, since it's widely believed here, that casual is mainly a guy thing and that women only do it in hopes of a relationship later, unless that is not correct for some?