Because all it takes is for one of these threats to actually pan out with dozens of people hurt or killed. Then the university would be sued into oblivion and get cornholed by the feds for having knowledge of a bomb threat and doing nothing, not to mention the scorched earth PR nightmare that would follow.
I know. That's why I added 'Not really' to my post, but it never happens like that. Still, there's a first time for everything; especially in this fukked up world we live in today.