Why does someone bother to be a professor if they don't even bother to correct tests properly?Good pension?
But there's more to your question than that, isn't there ?
As for public universities, I imagine having a lifelong job from which you'll only get fired if you neither go to work, nor send an intern and/or a yes-man to do your job, is appealing.
In the case that's bothering me, though, he is a good teacher, but it seems he doesn't read the tests. Grades for the first test were arbitrary, and for the second test, virtually everyone had either what they needed to pass without a final, or what they needed to get the right to do a final.