@voxofgod yep, thats why. Next time you see a "decent" number of boosts on a post and no likes, click the "..." And either "Open original page" or "copy link to post" and open it in a browser, I bet you'll see a significant amount of likes.
I use it as a sort of "I read this, but it might not be noteworthy enough to push to my followers". Then if I really want to "remember to go back to this" I use the bookmark feature.
However, likes don't do anything *for* the popularity of the post per se, unless you're on a bigger instance in which a lot of likes could originate from. In that case, they're used to populate the "trending posts" feature of Mastodon for that instance only.
Thankfully though, not many people care about post popularity here as far as I can tell.