I forgot to mention that I think this is as much a part of the consequences of changing gender roles. Women want to be treated as equals professionally (and rightly should be) but then in some cases seem to act that the new rules don't apply to relationships. Say what?
They still generally want that long term relationship to provide them with stability, security, and someone to listen to their worries for the rest of their life. They're willing (mostly) to offer lifelong care, including some sexual favors, to get this.
Well want doesn't get you anything. I want a pile of money for no effort but that's not gonna happen.
The idea of future sexual favors is quite meaningless and I do quite a good job of caring for myself. What else do they bring to the table? Seriously. What do I gain, what does it cost me, what are the risks? I can't ever see a positive value proposition.
Maybe I'll find that someone that makes me ditch my both negative view of marriage and it's position as a business relationship as much as if not more than a love based one. But I don't put the odds all that high.