Depends on your style of punting as well. Some punters like to give as well as receive pleasure, some just like to be "selfish" and its all about them. There is nothing wrong with either way, you are paying so do what you want. I know it feels weird paying for the privilege of getting somebody off - maybe we should get a refund!
For me, I love giving oral and wouldn't entertain a meeting that didn't have it on the cards. Maybe it is part ego, who knows, but I have honed my technique over many years and practised on a few "stubborn" regulars to get to the stage that it gets commented on by many of the girls that I have seen. It is a definite art that I like to continually improve. My bookings tend to be long ones though, so I can spend time on doing it rather than having one eye on the clock all the time. A bit of reverse oral at the end of a session usually makes the session overrun if they are enjoying it.
I am talking about part timers here and not full time professionals. I wouldn't bother with them.
When you get to your 50's and past, you don't get a lot of opportunity to bury your head in a slim 20 something so I am going to make the most of it