One of the most fascinating things about the Fallout franchise is the history of the vaults. Before United States was destroyed via atomic bombs, the government ordered the Vault-Tec corporation to build a number of underground safehouses. To the public, these vaults were supposed to help ensure the survival of the American populace after nuclear annihilation.
They didn't build nearly enough of them. Not to justify what Vault-Tec did, but in a way, building enough vaults to house an entire country is kind of crazy. So instead they only built 122 vaults—which, okay, still better than nothing. The issue is that the true purpose of the vaults is a nefarious one.
You know how most of the social experiments we hear about show that humanity is kind of screwed up? There's the famous Stanford Prison Experiment, for instance, where normal everyday men pretended to run a prison. Half of them became guards, half became prisoners. They didn't leave any detail out—prisoners got "arrested," the guards were given batons, and so on. It didn't take long before they all forgot it wasn't real, and the results were disturbing. The guards hazed and abused the prisoners, and the prisoners would have breakdowns. The experiment was canceled before it ran its course out of fear of what would happen otherwise.
There are other social experiments like it, in that they are testaments to our humanity—from how far we'd go to hurt others, to how long it takes us to go to someone's aid (if at all).
Many would argue that social experiments are inherently immoral and wrong. At the very least, if someone does something "as a social experiment" to get away with amoral behavior, we'd likely think that person is an ass.
While the war ramped up in Fallout, Vault-Tec became very powerful—practically another branch of the government. As cliche as it might be, that power corrupted them. They'd go on to research how to evolve humans with the FEV virus, along with a slew of other questionable weaponry and tech.
So it should come as no surprise that the vaults themselves weren't meant to help people. Actually, they were large-scale social experiments. Each vault tested certain conditions, often absurd and ridiculous, sometimes completely disturbing. Most of the vault-dwellers would never know this, save for the overseer, who had to make sure that everything in the experiment went according to plan. The purpose of these experiments was to test out how the population would react to certain conditions, and then to judge how the subjects go about repopulating the country.
In Fallout 1, we saw an issue with Vault 13 that was actually common amongst a good number of the vaults: the water chip was defective, and that's the reason your vault sends you on a quest. Nothing too crazy. Other vaults would have ludicrous conditions like "all women and only a single male." In Fallout 3, the infamous Tranquility Lane is a part of Vault 112, where residents are trapped in a virtual simulation that was maintained by the creator of the GECK.
Fallout: New Vegas, like all Fallout games before it, has vaults in it. Two are of particular note: Vault 21 and Vault 11. If you thought that a vault built in Las Vegas absolutely had to be themed around gambling, you'd be right—that's exactly what Vault 21 is, the gambling vault.
When you enter the strip, Vault 21 is nothing but a glorified gift shop maintained by Mr. House. But if you delve into its history, you find out that it was originally inhabited by only gambling addicts. The idea was to make the vault as "equal" as possible, and this meant that everything in the vault was left up to games of chance. The vault would be emptied by Mr. House after winning a bet against the residents of Vault 21, but you can't be too sad for them or anything. They left the vault for another gambling nirvana, New Vegas itself.
Vault 21 has one of the more amusing premises for a vault in New Vegas; Vault 11, meanwhile, is one of the more disturbing vaults. Here, the vault residents are told that they have to sacrifice a person from the population every year or else everyone will die. What they don't know: they're supposed to defy the decree, and if they do, the vault would tell them that they did good. Guess what: they don't figure it out until it's too late, and almost everyone is dead.
The story leading up to the downfall of Vault 11 is a tragic one. After the first batch of vault dwellers find out that the overseer knew about the twisted purpose of the vault, they elect the overseer as the sacrifice. The vault then adopts this as tradition, where all of its overseers are sacrificed after their term ends. It's funny, in a twisted way, to think that elections are typically characterized by a candidate's desire to be elected—but you'd imagine that in this case, people would campaign so that someone other than themselves would be given the overseer title, regardless of what power came with it.
Eventually a woman named Katherine Stone is told that if she doesn't have sex with a certain group of people, they'll elect her husband as overseer. She complies, only to find out that they intend to elect her husband anyway. She then starts killing those people off, supposing that at best they lose their majority and her husband is safe, or at worst she is elected overseer instead of her husband. She is right, and her first act as overseer is to abolish the election and to have the sacrifice be determined at random.
Naturally this upsets people, notably those who think that Stone's actions will destabilize the already-established power relations in the vault. This, in turn, catalyzes a war that leaves only a handful of people alive. Fate is cruel, and the last remaining vault dwellers find out the truth about the vault. They are so aghast with what they learn that they kill themselves... though even these final moments are filled with tension over what should be done. The only remaining evidence about these events are the audiologs that you find when you explore the vault years later.
You get the feeling that these social experiments were done because the government wasn't really interested in saving anyone that wasn't "important," (i.e., themselves) and this is reinforced by how the Enclave treats everyone on the wasteland as something other than human in almost all the games. Regardless, it's difficult to point fingers and be judgmental about it all, because this vault plot twist is exactly what makes them so fascinating. I know that whenever I play a new Fallout, I'm excited to see what new vaults the designers have thought up. My hope is that the Fallout in question features a good mix of funny vaults alongside upsetting ones.
Maybe we're just all awful human beings—that's what all these social experiments say, anyway. Consider this though: the Enclave might be the ones that set up the experiments, but we're the ones practically eating popcorn while we read the results.