Ilosar said:
THE LEGION IS NOT A SOCIETY.
So wait, it has a leader, a social structure, a clear hierarchy, it rules over 4 state's worth of kinda-sorta-civilians-but-not-really, yet it's not a society? K then.
Watch the movie The Postman, in which it seems the Courier and the Legion were inspired to some extent. That may help you understand his point. If you don't want, here's a spoiler about it:
[spoiler:9cc402fa40]The movie is set in a war devastated USA, big cities etc are gone, small settlements thrive on their own. There are no governments whatsoever, and the one force around is the Holsonist Army.
They come from time to time, take tribute and recruits, and go away. They have their own camp/base/HQ, where they do whatever they see fit in their daily routine (like training, as all armies do), and do not govern these settlements, nor interact with them in any way other than the previosly described (take what they want, give nothing in return).
Thus, the Holsonist are not a society. In fact, society will only thrive, in the area at which they are uncontested, if and when they are either removed or decide to effectively rule (even if in a... "North Korean way").[/spoiler:9cc402fa40]
The same goes for the Legion in Fallout: New Vegas. There's a leader, like all armies, but Caesar doesn't rule over the settlements in Arizona+other states, he just ensures no armed activity exist besides the Legion (thus no bandits, and safe routes for commerce, but it's not his goal; the absolution over the territory is his goal).
There's a hierarchy INSIDE the Legion, but it doesn't extend to the civil society (remember, the Legion has slave, but nothing was said of the settlements in it's territory; probable there are slaves in them, too, but they are slaves of the "free" people - farmers, merchants, etc -, not of the Legion).
There's no clear social structure; there's only the Legion's structure.
In short, it's a roaming army, not a society.
Life in this region may be more stable, safer than in a lawless wasteland full of mutants and raiders, but it is not a desirable alternative to what NCR tries to be: a rebirth of pre-war society.