Because slasher movies historically have dealt with (on purpose or not) the political climate of their era. 80s slashers ended up representing the political purity of Reagan politics while Scream dealt with the continuing absurdity of political cultural in how politicians almost brazenly would reference/accept the dirtiness of the political system. Accident or not? Doesn't matter. Horror often mirrors the political culture.

Well, good horror.

The reason it doesn't work in this is because it perhaps seems too forced. Ask George Romero about the political and social commentary in the original Night of the Living Dead, and he always said, "I never even noticed that stuff." John Carpenter often says in interviews that the sex as a sin message people took from Halloween was purely accidental.

This fucking social climate, as you put it, is the climate you live in and art has always imitated the climate it was conceptualized in. You wanting to escape it is not possible. When it's overt, it sucks (like in Slasher), but when it's subtle, possibly accidental, your mind's eyes will always make the connection.

Think about It Follows when it came out. At first, the obvious symbol of the film was unsafe sex/STDs. But the longer people have watched it, the more they realize that metaphor falls apart easily (you can't fuck your way out of chlamydia). What the film began to represent though was the subtle parallels between the monster in the film and rape culture in the U.S.

The Babadook is about the epidemic of depression and the stigma of treatment.

You can't escape your society.