Slightly different perspective here as I'm only into females, but I do indeed love it when I get a partner off with oral. The main draw for me is seeing her lose control, ideally both mentally and physically. It's always a personal victory (not to mention very hot) when a partner who's usually silent simply cannot stay quiet, and moans/groans/whatever. Same for things like thighs around the face, bucking, or pulling you down by your hair: making her lose her cool and civil behavior is amazing.