I was asked this question and thought it was amusing. I guess some dancers are not used to customers who smile a lot. One dancer in that same club even commented that she likes it when a customer smiles at her when tipping. Makes me wonder why other people go tip dancers if they don't even smile at the dancers or seem to enjoy it.
On the other hand, there is a possibility a recent hair cut I got made me look a lot younger than I expected. I'm not used to teenagers at the beach coming up to me and talking to me as if I'm in their age group.
I usually play dumb for exactly that reason - I want the girl to explain to me how things work, even if I have been there before. Not every girl will have the same explanation, especially when it comes to prices. That's often a good way to find out whether prices are negotiable or not.