Gunther is Luann's lead weight. Diane is the girl next door that Brad drools over. Puddles is Luann's dog, who just drools. Men are, well, silent and detached. Women are much more demonstrative and volatile, thus more fascinating to write about.
Guys are boring.
In most of my early rejected strips, the best characters were always the female ones. Plus, they're more fun to draw. Besides, you don't need to be what you write about. Jim Davis isn't a cat. Yes, art classes definitely help drawing ability.