Bad Jim said:
The real question is, why use bottle caps as money? How difficult is it for someone to make a bottle cap factory even in a post apocalyptic wasteland? There's no long term value in them at all.
You see, this is the problem with people coming into the
Fallout universe without knowing the lore, as well as Bethesda's problem for not explaining the elements of the universe.
Bottle caps were first found in the original
Fallout. The reason that they were considered as currency is because they were stamped and backed by the water merchants in The Hub. When it became possible to produce metal coinage again, they changed to that, leaving bottle caps to become worthless again, as we see in
Fallout 2. Indeed, there's a playful allusion to this in one of the quests in Broken Hills, where somebody claims to have a fortune hidden somewhere in the town, and when you find it, it's a collection of 10,000 bottle caps - which would have bought you a suit of Combat Armor, along with a decent weapon and some ammunition in the first game, but which is worthless in the second.