If I was working a cushy admin job, I'd need way more bribery than $5 worth of coffee and doughnuts to intentionally select a worse vendor, especially if the decision would negatively impact my colleagues and get me flak.
>Why is it so hard to imagine people who work in education would have flexible ethics for personal gain?
Because if you read the other comments, there are perfectly reasonable explanations that don't involve graft. Jumping to "bribe" every time there's bad behavior is just lazy thinking and means you don't actually figure out what the root of the problem is.