I agree with you, but i expect money has something to do with it. Look at the way Eel Marsh House was decorated in The Woman in Black. They did a fabulous job making that house creepy, but it had so much stuff in it! Antique toys and such. That is cumbersome and expensive to do, especially if the haunted house is seasonal. And if you are herding people through it, someone might shoplift an item or two. It is way easier to have the costumed folk jump out at you.
When my older son was in grade school, the city Dept. of Parks & Rec used to haunt a pioneer village in the middle of downtown. That was the best haunted attraction I have ever been to, because it wasn't just a house, but a whole village, with trees and such. The pioneer village is still there and is used for various festivals throughout the year, but now they do the Halloween bash at more of a wilderness park on the Southern edge of town. You stand in line forever for a "haunted hay ride." That is fun, too, but it doesn't last quite as long as the lantern-light stroll through the pioneer village used to do.
A local chapter of storytellers (calling themselves the Borotellers) offers a lamp-lighted ghost tour through the historic district in October. That is a lot of fun to do. The story teller will dress up in Victorian costume, as our historic district is mostly antebellum.
There is also a Civil War battlefield here, called Stones River. Throughout the warm months and into October, they offer a free "Hallowed Ground tour," where they guide a group of about 35 through the cemetery. It takes place at dusk and, once again, you are led by lantern-light. People who work at the battlefield costume as people from the Civil War era, and they read letters beside the graves of the people who wrote them--or, in some cases, they are reading the letters of family members who were writing to the people who are buried there. It is quite an experience. As I said, it is free, but you have to make reservations in advance, because there is no electronic amplification, so the group cannot exceed 35. Any bigger and people wouldn't be able to hear it.