Uh, you do realize that most Ghost-lore is based on peasant remedies, right? Salt, silver, knives, etc. all were codified in medieval/renaissance/early modern history. This is the level of technology that rednecks live at. It makes perfect sense.
Except for No Exit, Nightshifter, Phantom Traveler, Skin, Faith, Tall Tales, Malleus Maleficarum, Red Sky at Morning, Mystery Spot, Jus in Bello, Monster Movie, Hollywood Babylon, and half the episodes of seasons 2 and 3.The show really revels in the idea that large cities don't really exist. In that large cities don't exist, and that every town they go into are small, out in the middle of nowhere, towns. This is again, to justify the plot that the Winchesters can get away with everything they do.
Did... did you watch the show? A major theme of all series is that the Brother's aren't getting away with almost anything... it's just that they're so mobile that the FBI and police forces have trouble catching them when they come into town. Even the pilot has an instance of the Police managing to catch them. This is a major theme. You cannot watch the show without noticing that the Brothers stick to smaller towns and the outskirts of suburbs (Like Malleus Maleficarum; Hell House, as you pointed out, was a big research failure) because the police forces are less likely to collaborate with the FBI and regional law enforcement.
"Nightshifter" ends with Dean literally saying "We are so screwed" because they realize the FBI is on their tail. It's a major plot theme throughout the second and third seasons. The question of "how do they get away with it" is a major theme throughout the entirety of the first five seasons. It's a constant interplay. Did you watch the show?
Yeah, because the main characters are Americans who don't travel outside the Country because they have so many felonies attached to their names that they cannot get passports without being picked up by the FBI.The other problem, of course, is that the forces of heaven, hell, and beyond only seem to operate in the US. You will never see a monster, ghost, demon, or some other thing anywhere outside of the continental US in Supernatural.
I don't think you watched the show.