Is this a stand alone tennis club, or part of a golf club? And are you a member?
I can’t speak for stand alone tennis clubs, those cater to a possibly poorer demographic, but at every golf club I’ve been affiliated with, it’s customary to tip your golf or tennis instructor.
So the question is: when you’re sitting at a bar and the attractive bartendress starts making eyes at you, do you think she’s trying to get you to leave your wife or to get an extra 10% tip out of you? Your answer to this question says a lot about your personality.