I think having it while hiding it from public makes a lot of sense because it felt like there were at least some places where
1) there were campaigns from people to get as many dislikes as possible
2) there were media outlets turning this into stories "so and so is the video with the biggest like/dislike ratio!" or "so and so video has the fastest climbing number of dislikes in the first 24 hours"
Which to me will always encourage people to game the system as opposed to trying to be a reflection of people's natural reaction.
Having the button still there and the results being visible to the creators of the video still gives them feedback on how their thing is coming across without people turning it into a sport where they try to outdo each other with higher scores.
(for the record: I have a similar loathing for the "trending" thing on twitter, especially considering how easily it can be gamed and again how many people try to turn twitter trends into "news" stories)
That said, the more interesting question would be: what if you made the like numbers invisible as well? The platform could still consider them in their algorithms and show them off based on high number of likes. But there is no doubt people would do less liking if it wasn't visible and the platforms in the end selfishly do want engagement from the user.