Help with Child Support?

Im not trying to start any fights here but will someone please help me justify this line of thinking. Why do I commonly see "single moms" who's babies father wants to be an active part of thier childs life and raise that child to the best of his or thier ability only to be all but banished from the kids life b/c the woman no longer likes the man.... then, and here is the real question: She typically demands this guy to pay child support as if its her right even though she just denied said support and is willing to "legal up" to get already something he was wanting to provide whole-heartedly in the beginning. Is it all about the money?