Facebook users do not want their news feed to be filtered. That's why the UI keeps automatically flipping "Sort: Most Recent" back to "Sort: Most Relevant", and why so many users keep asking how to STOP it.
So, FB users want to see the content, and the content providers want them to have it. The only problem is an artificial scarcity created by FB. That will eventually drive users away, to other venues where they can get what they want.
By contrast, Google's advertising only adds to users' experience. Users generally accept it, either because it's a mostly harmless distraction, or because it's actually delivering extra content that they would not otherwise have seen.
It's analogous to saying Google users don't want their search results to be sorted by relevance.
Most Google users NEED Google to sort their search, and Facebook is doing the same thing.
And hey, search on Twitter lately? Twitter only shows you SOME of the relevant results in the default view (top results). You have to click "see all" to see them all. Everyone's doing it because it HAS to be done to show you things you are interested in vs spam.
And don't you hate how only the best stories appear in the default view of Hacker News? Of course not. You can go to the "new" tab if you want, but most people don't.
By keeping the filtering process opaque, FB have concealed the value of what they do, so users don't appreciate it. Now, they are fiddling with the unwanted, secret algorithm in a way that benefits them and hurts users - not a good long term strategy.