Arguably, reasoning why to go to university feels more like rationalization rather than supporting evidence. It's definitely not physics.
On the other hand, believing that your actions have consequences, and that you will pay for your mistakes, is a very good assumption. But in the sense that you mention, it's "unsupported". This lack of evidence may lead me to conclude that societies are hung by a thread, and that collapse is imminent. It could be, but societal collapse simply hasn't happen after an unexpected, global, unprecedented turmoil.
Why some assumptions are "better" than others? THAT is a very good question. My take is that there aren't a priori: some societies believe some assumptions, and survive, and others don't. In a sense, to me, assumptions are only good in retrospect, and it's an idea that "feels" correct rather than something I can "prove".