It’s one of those things in-game that just doesn’t have a logical explanation. The whole point of Cata DDA (in my opinion at least) is this crazy, hodge-podge collection of every B-movie horror trope ever made, rolled into one big shitstorm which our survivors are (unluckily) stuck in. While a lot of the more major things do have lore to go with them, there are smaller things (like this) that are just plain there.
I think a lot of the complaints we get about items are rooted in the fact that some people see the game as a lot more serious than it’s actually intended to be. This isn’t “The Walking Dead”, this is the CATACLYSM, the shit has hit the fan in EVERY way physically possible (and sometimes in ways physically impossible), and the survivors are just going to have to deal with it.