For the same reason I make my 7 year old go right before we leave on a road trip. I want to log as many forehands (I mean miles) before I have to stop again.
FWIW ... I play with a guy that stops to pee every 8-10 games. All of us have asked him to go to the doctor and have his prostrate checked. He refuses ... after all he is a health teacher, he should know whats best for him.
"You should be playing linebacker, not singles."