Sort:  

Everybody thought that the ones who made camp number 13 were pushing their luck, and many builders quit for superstitious reasons.

Can't argue with that logic.

When I was writing the story, I made the premise that the experimental towns were built by a government that was run by dark occultists, since the story was meant to mirror real life in its structure. I still don't really understand all of the numerology and stuff, but the number 13 seems to come up a lot for some reason, so it went into the story.