It may not make sense to you but, a place like that actually exists in the real world.
There is an Amazon tribe that chase their toddlers into the jungle after telling them to walk in a certain direction without them knowing why, if they succeed doing so without dying (it's a frikking jungle after all) they reach the "child" village where they live until they get too big. advlts never set a foot in the "child" village or helps them any way.
Sparta also send their children into the wilderness to see if they can survive and to beat the weakness out of them.
Bottom line is that we westerners have a hard time believing something like this is even possible because we're all a bunch of pussies trying to act though.
Except that in Fallout 3, no one that we know has been sending the kids to this cavern on the ass-end of the wasteland. How they get there is left up in the air, and it's demonstrated that the Lamplighters do NOT accept newcomers easily (you have to convince the Mayor to let Bryan Wilks in with a speech check, if you opt for that). And as I've also said, Little Lamplight is just outside Vault 87, the main base of operations for the Super Mutants, aka the big guys who actively hunt down and kill/capture any human they come across. And as the Murder Pass area shows, said mutants have managed to invade Lamplight territory, and the only thing between them and the kids is a flimsy wall made out of random detritus that, game mechanics aside, could easily be smashed down. Even ignoring the mystery of how Lamplight has been able to maintain a population for two centuries, it should have been long ransacked.
I'm also going to have to ask you for some sources on that Amazon tribe. Smells like absolute [censored] to me.