I think it's that paranormal is a genre that's considered to be overdone and stagnant, though I believe it's more of an issue of writers copying ideas rather than coming up with their own. As a result, someone comes along with a zany idea like bull shifters and, well, a publishing company jumped on it while ignoring how poorly executed it was because, hey, people will apparently shell out five bucks for only 20,000 words, and they might do it nine times over because, hey, this is a nine-novella series.