There are a handful of well-paying (semi-pro and up) fiction markets which exclusively publish horror tales. Go ahead and give Duotrope a good search and you'll see. Some of the best stipulate their dislike for the 1st person POV in their guidelines.
My favorite mode in which to write is 1st person, and some of my favorite horror tales are written with a participant narrator. Think Edgar Allan Poe here, people. Think H.P. Lovecraft's "The Rats in the Walls".
I understand why an editor would want writers to steer clear of the 1st person. I'm sure they've seen enough poorly written, serial killer narratives (or even the ghastly "I die in the end" stories) to choke a proverbial horse. But when the 1st person is done well, a story holds even more sway over my imagination.
Which brings me to Mr. Gaunt and Other Uneasy Encounters by John Lagan. I'm only two tales into the collection ("On Skua Island" and "Mr. Gaunt"), but Lagan has a way with weaving a 1st person story ("On Skua Island") which really left me with the chills. I ran up the stairs from my darkened basement on the way to bed after reading (I have no shame). A 1st person narrative has a way of drawing a reader into the story that doesn't always happen in a more objective POV. When that narrator tells his chilling tale and ends with "I'm feeling rather uneasy tonight," well, I am too. Mr. Lagan's prose is rather thick if not outright baroque, but he has a solid sense of pacing. He plants a seed early, and when the reader returns to find the fully flowered monster, wow.
So editors, I understand. I know the pitfalls of poorly written 1st person horror. But please, please be willing to see the benefits of a well-crafted tale, regardless of the narrative POV.