This, I think, is what we're talking about. Not, "could it be true?", but rather, "do we have any reason to believe it's true?"
That's what evidence is. A reason to believe. You could say, "well, we don't need a reason to believe." But you do. You obviously have one. there are too many possible beliefs, there has to be a way to distinguish between them. Pulling one from a hat at random is a possibility. As is believing the one that is the most attractive.
I prefer believing the one that I judge most likely to be correct. And the only way to do that is to weigh the available evidence.