Wow there is just soooo much wrong with some of the posts in this thread but im going to start with this one, its got to be the best.
First of all their not disorganized, or lazy, i'll give you whiny because of the whole nuclear winter thing, and they only get dunk and gamble away their on money, not funds, when they're on leave and can go to the strip.
Really? Look at Ranger Milo who complains about the troops he's with outside Nelson. Look at Camp Golf where the 'wash outs' are put. Look at most of the soldiers being childish and boohoo about the simplest things. Also, their money ARE NCR Funds, derp. What pays for soldiers money? Military/government funds. NCR is pissing it's money down the drain, courtesy of the famous NCR tribal 'Head-In-Butt' Kimball. Things are so bad in NCR people are going East to MAKE money, speak to the gun merchant at 188, she states that the Prospecters you see are NCR citizens to poor to pay the outrages taxes back home.
They're perfectly capable of keeping their own roads and territories safe, it just so happens that right now the Mojave is the front line of a major war so of course things are not going to be perfect. You couldn't walk down the streets of Berlin during world war two without getting shot at and its not really a good idea to do it in Vegas right now either.
You answer your own complaint. Their OWN roads and territories. The NCR are foriegn invaders, no matter how you try to justify it, plain and short.
And how is the NCR going to get "demolished" by House or the Khans? Without the courier House is about as threatening as a pissed kitten because he doesn't have anybody to activate his securitron army, and the Khans are huddled up in Red Rock just hoping that the NCR doesn't come to finish the job that they started.
Funny, I could say the same about NCR. House could find another person to do his bidding if he tried, but when will the next all powerful super human like The Courier come along to play Atlas to NCR's occupation of a foreign land?
Its like I always say, all the people who hate on the NCR should think back about five years prior to New Vegas when the Legion first invaded, if they hadn't been there to stop them they would have rolled through Vegas, hung House from a cross and enslaved everybody else.
So you say, we don't know how things could have played out.