Well, it turns out that they have learned their lessons, since as those links will show you, each one of those movies had a fraction of the budget of a normal blockbuster but still made big money: Last Exorcism cost $1.8 million and made $67 million, while the comparatively pricey Ouija cost $5 million and made 18 times that.
The problem is that "viral marketing" is all the rage, but "viral marketing" doesn't have to have anything to do with the actual movie. There was neat Ouija marketing that involved a fake psychic pulling pranks, and by "neat" I mean "significantly more entertaining than the movie." Yes, I saw Ouija. I am not proud.
Why are those so much more successful? It's because even though these cheap, shitty horror movies that no one cares about get a fraction of the production budget, their marketing budget is on par with most other blockbusters. It's the clickbait approach to cinema: They put all their effort into getting butts into seats and ignore the quality of what those butts end up watching. Then, when the aforementioned It Follows (so goddamn good, you guys) ends up being a success because everyone who sees it tells everyone else how great it is, they keep looking for the "trick." The "secret" that garnered so much success for a movie that was made so cheaply. Gosh, what ever could that secret be?