To address the previous:
I was referring to the people of the vault. No one goes into a test tube willingly, particularly in cases as extreme as these. Though they were not told that a fake AI was used, exactly what "bait" was used? The bomb scare? And surely tests are completely pointless if there is no one to collect the data after a certain point.. to observe the effects on the people. Both the people AND the robot would have to be removed by an external force for the test to be complete. (be it a human force or otherwise)
Though the robot undoubtedly could collect some first hand data, there is no telling what is to occur. The robot may not survive the test. ergo, it is also part of the test, and the whole thing must be retrieved, the vault examined etc. However it seems like these people were left to their own devices. Who/what is running this test and why was it not followed through?
On the note of "ghoulish how?"
Perhaps this is a biased of mine actually. I just don't see ghouls, especially ones that spent that much time in such a place, as altogether human. Yes they have a back story, yes they are human in concept, but they've been twisted.. changed. And they've had plenty of time to adjust to it. While they may live in a city, I would think it would have some unique characteristics about it that may not be found in a town like Megaton. Something that jumps out at you and says, "This town is different.. ghoulish even." (besides the ghouls themselves)
Underworld:
In the defense of underworld, it is different, and does have a sort of hanging sense, having been set up (ironically) in a museum of death. It's also a special case. There aren't many down there overall.. they sort of just trickled in and stayed. They also didn't build the place themselves. They have no where else to go, and unlike a full out town like this, can't explore or branch out much. They are like rats trapped in a cage, just scrapping together a life, because there is nothing else to do.
Though they have a few scouts, few leave the area. It's as if it doesn't occur to them that it would do any good. They are more than simply out numbered. To even try would mean getting past the hell of mercs, super mutants and any other wack job they meet.. only to be faced with a human public who looks down on and fears them..
While it is true Underworld prolly has more npc's, your town, "Generation" stands to grow. (in theory) They only fight among themselves and other outcasts like the bandits.. not to mention, they have a keen set up. It would stand to reason this would be reflected by more open expression, and more than a few raider armors and weapons. (they do fight them )