Ooo, a hot new trend! Pirates are all the rage!
Which means that for publishers, who are looking at what the market will be like in a couple years, pirates are essentially over.
Couldn't I get some scary stories, please?
(But before you write some scary stories, go read a book or two in both the Goosebumps series and the Scary Stories to Read in the Dark series. And then contemplate how different they are--and how successful for two very close age levels. Tolerance of creepiness, just like sense of humor, develops rapidly between certain ages. Get it right.)