Ask HN: Why does Facebook keep unliking my liked pages and hide posts?

This is not a new thing but it seems like Facebook has been doing this for more than 4 years now, I would not see the posts from the pages I like and whenever I eventually remember and try to see my likes page, I would find out that the page has been automatically unliked! Is this some kind of a trick done by Facebook to blackmail page authors to pay for reach? all I see now on my feed is promoted posts and a few friends posts!