Ok, I didn't have time for a proper reply last night - hence the flippant comment - so to answer your question properly...
In theory, yes - although it's never quite so simple, is it?
Generally speaking a guy can get a BJ, he cums and it's all over and everyone goes their separate ways - if a BJ is all that was on offer that's all that happens. But on the flip-side, how often would someone go down on a lady without expecting it to lead to more - even just from the guy's perspective... all that effort and he doesn't even get a handjob out of it? I haven't yet come across that guy! This fact also probably contributes to an ingrained Pavlov's-dog type response from women, whereby a guy could make us cum 100 times eating pussy but we'd still want him to fuck us too.
Happy to be proven wrong though! ;)