Yes, the "cover reveal" is about exclusivity. Such as when covers are revealed on EW, they include the site's watermark. (So I don't share them until I find a version WITHOUT a watermark.)
This goes against all the talk about supposedly being "inclusive". Sometimes the author or publisher are the first to reveal. Bigger name authors reveal via EW. Some do it through one select blog. Others have a "sign up to join the cover reveal" blog blitz.
Soon a "reveal" becomes less about the book (which should be the priority), and more about the place it's being revealed on (note the obnoxious EW watermark).
So yeah, there's a lot of popularity politics that goes on with cover reveals. But pretty much as soon as it's revealed, a fan uploads it to Goodreads so people don't even have to visit the exclusive reveal site in order to see it ;-)