They actually did on at least 2 occasions and one was dangerous as the mascot was a live wolverine acquired by Fielding Yost. It became uncontrollable. Then there was Willy:
Fans complained that he blocked view of the game play. Previous AD Dave Brandon did say:
"I'm struck by the fact that when opposing teams come to our stadium, and they bring a mascot, all of our young fans are lined up to see if they can get a picture taken with it, whether it's the Penn State Nittany Lion or Sparty," Brandon said. "That's a little annoying to me. You can't get your picture taken with a Block M. Mascots are really embraced by the youth demographic, and we want to take advantage of that, for all the reasons that are obvious. ...
"We're interested in doing a mascot but it has to be something that fans love, that children love and everyone can embrace."
If for anything, do it for the youth movement, not for the grumpy old people.