It does also happen that people get stuff to review and have to send it back of course.

Sure, but that’s still not free. The company is spending time, money and resources on soliciting the reviews, sending units out, receiving units back and then scrapping or selling those units as refurbs/open box. They’re not spending that money unless they think it’s going to drive sales / awareness. It’s still advertising.

So the company that can afford to send the most stuff to the most reviewers win?