I always consider it a total treat, but there are so many guys that just don't like getting cum in their mouths.
I was in high school the first time a friend went down "after the deed". We had been at a party, and I gave him a great bj, swallowing every drop and letting him see the mouthful.. I have always found that to be sexy. Anyway, on our way back for him to drop me at my house, we stopped at our local park and had a great fuck, and he filled me. I just had this urge of it "not being over", so I got up and started to put my vagina right over his face, and a little cum dripped out. He objected, and said it was gross. I sat on his chest and asked why he thought it was gross, and reminded him of how much of his cum I'd swallowed since I knew him. We chatted, and he calmed down about it. As I mentioned, I was sitting on his chest, and leaking cum onto him. I scooped some onto my finger, and licked it clean. I scooped another little bit, and asked him to try it - he said OK and I just rubbed it onto his lips. He licked and swallowed, and he looked surprised as he said it didn't taste as gross as he'd heard. So I scooped up quite a bit more, and put my fingers into his mouth, and watched his face as he swallowed. I asked if he'd like more, since I was sure there was a lot left inside me. He said OK, so I turned around, and we 69'd. He came in my mouth again, and I think it was the best 69 I'd ever had to that point.
I turned him on to his own cum, and after many of the bjs I gave him from that point, we snowballed and he was really into it.
Other guys since then, if they want to snowball after a bj, I'll ask them to go down on me after we've fucked -- it is really a nice feeling.
But I've been surprised my entire "sexual life" at how many guys have not done it, and how many are dead set against ever doing it.
