ends up being a huge waste of time because the vast majority of companies are not going to be interested in you no matter how interested you are in them.

I mean, I've offered to work for FREE (either on part-time basis or for a few months) for many companies that I really wanted to join and appeared to need my skillset, and guess what? Not a single one of them ever invited me on board.

But I agree that in theory, in some instances, informed and eager candidates can look a little better than others if I'm doing the hiring.