I could be fired tomorrow as Dean of Faculty. You can't get fired over differences of opinion but administrators can. It holds down salaries. Reform of tenure is happening everywhere. Hampshire College has a variant.
All instructors have 'lecturer' positions with ten year contracts.
The problem with tenure is that departments may not function as well. Younger professors are more subject to elders. If they don't like the committment, it's hard to get tenure. Tenure stops an administration from exploiting people. I'd be in favor of some sort of revamping of it.