If you're fucking a girl, or she's sucking your cock, what do you want to do with your cum? Pull out just before you're about to pop and ejaculate into a towel? That's about as anti-climatic as finishing an expensive meal with a popsicle for dessert (it had best be one damn good popsicle, but that's doubtful). Nope, you want to see whatever you're fucking, either her ass or cunt or mouth, covered in your cum. You don't want to waste single drop, and she shouldn't either. If fucking were a work of art, then cum shots are the artist's signature. After you've fucked that asshole raw, you definitely want to squirt a hot load of cum all over that ass. It let's her know that you were not only there, but you dominated that shit and made her cum a few times. When she's sucked that cock so hard that it makes you cum, damn if don't want to turn her face into a Jackson Pollock painting. We're pretty sure Pollock was a fan of huge cum shots, too.