The source – blog.youtube
YouTube is trying to promote respectful interaction between viewers and video creators. To that end, in early 2021, the team experimented with a "dislike" button to see if the change could help better protect content creators from harassment and reduce attacks.
As part of that experiment, viewers could still see and use the dislike button. But it was found that because the counter was not visible to them, they were less likely to click the dislike button. Another reason was complaints from content creators of smaller channels - they were more likely to be unfairly targeted by fans of disliking.
What will change for video creators and viewers
As a metric, the disliking will not be disabled. Creators will still be able to find accurate data about their numbers in YouTube Studio, as well as other existing metrics, if they want to understand how their content is performing. Viewers can still dislike videos to customize their recommendations, but they will have to privately share feedback with creators. And also probably focus on the views/links ratio.
