You guys JUST realize that the Fallout games have less NPC's than it looks? Look at the vaults! Supposedly 1000 dwellers in most of them, when you escaped Vault 101 there were no more than maybe 20 in the whole vault. Remember, the world ended, so you can't expect Vegas to be the way it is today, in a post apocalyptic world. I would rather have 30 NPC's that I can actually keep track of when I need to, than spend hours looking for them in a crowd in about 7 casinos.
But it just feels so empty.
Maybe it's more practical to only have important NPC's around but it's also very weird to enter the most popular casino and find 10 people.