Sometimes, when a girl doesn't want to do more than the actual service and if the customer keep asking for more. Then the girl can just ask a higher amount of tip, just for the customer to stop bothering her for more service and stop asking about it. Also, not all the girls will offer the same amount of services, for the same amount of money. If the girl is tip hungry, I will just say no and will not choose her next time. It's her loss.
I have been going to iu, since they opened and the girls never ask me about money , even after the sessions. There have been several times, I had to say, wait don't go, I haven't given you your tips
So good luck for your next adventure.