Earlier quoted context omitted.
Conversely, why wouldn't someone believe something if there are no consequences to being wrong? As you say, unless you regularly dance at the bleeding edge of material science, nothing you believe really matters, so why not jump in with both feet?
Eventually such a practice will bite you in the ass when you form an opinion on something you think doesn't matter, but actually turns out to matter.
So yeah, if you act irrationally, you will make bad decisions. But it's not irrational to believe something loosely based on a very limited set of facts.