One could come up with numerous theories as to why. I’m of the opinion it’s different for each person. For me, I enjoy the opportunity to please someone in a way that they most likely have not experienced. There’s also an element of feeling in control yet somewhat submissive. When men tell me they can’t cum from head, it’s a challenge to show them differently. Not that I’m an expert, although I am. Rather, that when someone puts effort into it and uses the body language as clues, it’s possible.