This OP's question reminds me of a child who is growing up and asks if Santa is real or not. Despite all the evidence to the contrary, they want to believe Santa is real because it's a nice story and they get lots of stuff that makes them feel special (eg presents). So our ego wants to feel like we're masculine enough to satisfy our partner and for some folks that becomes the holy grail. Let's be clear here, I'm not suggesting OP is a child or falls under this category, but there are guys out there for whom this would be true.
At some point, a kid in the school yard (ahem, maybe named Fiona) says "Santa's not real," and then for the kid a bunch of stuff doesn't compute: how do the presents get there? Who eats the cookies and drinks the milk? Who writes the note on Christmas morning, if not Santa? What about the Santa tracker on Christmas Eve? Then they start thinking about reality: how is it possible to get down the chimney? What about kids who don't have chimneys? Wait, reindeer don't fly. And reality kicks in. Shit, no Santa.
Santa's a fantasy and so is hanging out with a hot woman would otherwise not be willing to bang us without $$$. Pleasing her, bringing her off, CIM, COF – or whatever you kink – is part of the fantasy. And to Charlee's point, we men - who are often in a cycle of perpetual childhood - want to know if Santa is real. But we really don't. What we're really asking is "I brought you to orgasm, but not those other guys right?" We're looking for some kind of validation that it's not just about the money; that somehow the provider enjoyed themselves too because of something unique about us.
I agree with Charlee and Fiona that when you are communicating with a provider at a higher level then the likelihood of making them cum is much greater (if that's your thing). I know for me, the session is always more gratifying when my partner cums. It's not the fact that she reaches orgasm, per se, but more that it's an indicator that we connected at a deeper level than just inserting A into B. These days when I visit a provider, I'll just let the session unfold; engage in some conversation, learn some boundaries, maybe some kinks. And sometimes Santa shows up and sometimes he doesn't. Most of us, after all, are just kids in bigger bodies – same insecurities, just bigger piles of it.