Hailey, the original woman host wasn't a sex symbol. Yes, she was cute, but she also created and still produces the show. So, whileyou are right that in most cases they just need the "Sex Factor", that'* not how Kathy got the job. I have a feeling when she started hosting during season 2, she just said "Okay, it worked. I wanna play".
PS, in case y'all couldn't tell, I'm a HUGE fan of the show. Even got 100% on the trivia game on thier site.. All together now "Nerd!"