According to Stephen Fry:Supernatural manages, The X-Files managed. I think a lot of it is to do with how much filming is done on location, probably something to do with our labour laws too.
"It’s a very odd thing, American television. Because, well, you know, they make 24 episodes and you’ve got about seven or eight days to do each hour episode, or an hour minus the commercials. And they have very little time, but they have a stupendous amount of money. So, simply, anything that goes wrong they just throw another camera, another crew... And at three in the morning on the FOX lot, for example, it’s busier than at three in the afternoon."