Because its fun to win, I think...I wouldn't know I've never won anything (well I was on a
#1 ranked video game team in the world but that's different).
As a guy that doesn't win much, I think its important to move people on fast; its not uncommon for 3 guys with points to be on the podium, meaning the 4th,5th, and 6th guys are denied points and frustrated. In the SCNCA 4's, it always seems like we have enough racers with p12 talent to fill the podium and its rarely a race full of racers with Cat 4 talent. I may catch some flak for this, but IMO if you're sandbagging 4's and winning most of your races, chances are you will be competitive in the 3's and in many p12 races (ie not Dana Point, Manhattan, San Rafael, etc).