Why you should never date a tennis player?

Here's a joke related to why you should never date a tennis player:

Why shouldn't you date a tennis player? Because they're always aces-sing around!

This joke is a play on words, as "aces-sing" sounds like "messing" and refers to the term "ace" in tennis, which means a serve that the other player can't return. The joke implies that tennis players are always playing around instead of being serious about dating.