Yeah, I had a guy exclaim in utter astonishment "YOU'RE KIDDING!" when I declined to rim him. Um, it's not advertised in my services and I'm pretty sure that licking anuses is not a standard thing that one assumes all prossies will do.
And, the guys who, upon being told that you're all booked up for the evening say, "Can't you just squeeze me in for a half hour?"
"No, I don't think the client who is coming for two hours would appreciate that."