So if you have access to a large number of highly skilled people, and you really don't absolutely need them to do other things, why wouldn't you force data labeling tasks on them?
Facebook is also planning a 10% layoff, so this also works as encouragement for people to leave voluntarily.
(Before you downvote me, note that I'm not endorsing this or saying it's a good idea. I'm just saying that I believe it's true, because I can see how Facebook's leadership would think it's a good idea.)