Q: Why did the hamburger always lose the race?
A: It could never ketchup!

Explanation: Ketchup is a thick liquid made from tomatoes; Ketchup is made from tomatoes.  Many people put ketchup on their hamburgers.  To “catch up” means to get to the same place as the person who is ahead of you.

“Ketchup” sounds like “catch up” and if you can’t catch up you can’t win the race!  Silly joke!