As President Richardson made clear, the people in the vaults were irrelevant. In the Enclave's eyes they aren't *people*, they're subjects.
Truth. The following is taken directly from Fallout Bible 0...
"...the federal government (or whatever branch of federal government was responsible - it was not necessarily the Enclave) may not have ever considered the Vaults as society's best chance for survival - the government may have considered themselves the best candidates for rebuilding the world and already had their asses covered in the event of a nuclear or biological war by relocating to other remote installations across the nation (and elsewhere) that weren't necessarily vaults. The Enclave certainly didn't seem to be devoting much effort to digging up any other vaults and trying to use the human stock there to rebuild civilization."
"Nonetheless, even members of the Enclave probably could not answer the question of who created the Vault experiments and their reasons, as many of the people responsible for the creation of the Vaults died long ago, and many records were lost in the great static of 2077. President Richardson was familiar with the purpose of the Vaults, but he never saw them as more than little test tubes of preserved humans he could mess with."
"Basically, the Vaults were never intended to save the population of the United States. With a population of almost 400 million by 2077, the U.S. would need nearly 400,000 Vaults the size of Vault 13, and Vault-Tec was commissioned to build only 122 such Vaults. The real reason for these Vaults was to study pre-selected segments of the population to see how they react to the stresses of isolationism and how successfully they re-colonize after the Vault opens"
Also in the bible is stated that in Fallout 2, with a successful skill roll, the player is able to uncover classified files on Vault 8 and Vault 13's intended purposes for vault experimentation...
"The player was also intended to apply his Science skill to the central computer in Vault 13 to obtain a history of Vault 13, the Overseer's involvement in the Vault Dweller's expulsion, and even worse, the true purposes of the Vaults. The Overseer was conscious of the true purpose of the Vaults as social experiments on a grand scale, and he drove out the Vault Dweller because he was afraid that he would ruin the experiment... or uncover it."