There's no money in having inconvenient truths laid out in the open. I see the same stuff on instagram and facebook when pages share content without crediting the original author. The laziest effort to credit the original art work is a "ctto" credits to the original author, something like that. When called out about the behavior, it's either the image is taken down, comment hidden and blocked, or claim "oops we forgot for the nth time". There are less repercussions in creating practices like these on social media and more money to be gained.
Original content creators can't grow their pages fast because content takes time to work on, the good ones at least while the content thieves can have access to a wide selection of content creators anytime. Hive's downvote tool is one of the best damn thing ever implemented.