Because they can be knocked over and get shattered!
Alabama Crimson Tide's crystal BCS trophy is shattered in mishap - ESPN
For a program that wins championships, you would think their players would have enough coordination to avoid tripping into the trophy!
"Hey ya'll, jus tape'er down, yule be fine."Charley Green, trophy manager for the American Football Coaches Association, said he uses adhesive tape to secure the ball when it's toured around the country and advises universities to take the same precautions when displaying it.
"It's pretty fragile, I guess," Green said. "It only weighs about eight pounds so I can see where if it gets bumped it would roll off."