Sure, they're conquest is flawed and bureaucracy is slow, but its still effective. It shows by them being able to pump water and run power to the strip and try to protect the Mojave against slavers. Yes, they are lacking in support in the area and spread thin but given the opportunity, they would step in and protect more of the Mojave than they do without the couriers intervention.

From the start of the game, they are keept trading lanes on the safe until recently due to the legionary wearing away at their numbers and Oliver Gathering them all at the dam. They built a camp outside Primm to minimize the unfortunate situation. With intentions of ending it but improper support to do so. After the town is cleared of invading forces, they would be willing to protect the so long as the citizens agree to it. Though due to the town's lack of government.. it is by martial law and they do get taxed. But after the events of the game, if this is what happens to primm, the NCR makes them one of the biggest stops off the long 15. But they're also actively employing wastelanders outside of the strip at the Quarry and at the sharecropper Farm and build refugee camps. Refugees of their campaigns, of course but house would not build refugee camps and neither would the legion.

Caesar's Legion would be able to maintain and support civilization but their totalitarian dictatorship is obviously oppressive unless you're going for an evil playthrough. They too would keep the tradeing lanes "safe". But rather than employing wastelanders they would enslave them. They would have the support to clear the town of Primm but their totalitarian dictatorship isn't any better than martial law.

House never has any intentions of helping any wastelanders. He brags about the hundreds of thousands of caps he spent to find the Platinum chip but noticeably never talks about any aid efforts he funded. He has also never once tried to provide the followers with medical information to gain popularity and favor in the eyes of the wastelanders and even continues to hoard his information if the bug is detected. House would never let himself be voted from power, nor would he be interested in representing wastelanders. He has plans for a violent power grab by attacking the victor of the Second Battle of the Hoover dam and on top of all that, he has problems running his own strip. Important entities on the Strip planning against him.. legionary spies roaming the strip.. House is far better off working with the NCR. They're the most likely faction to be intrigued by his technological aspirations and most likely to allow him the resources and support to work towards those goals.

None of the Allies you would build in the event of an independent Vegas would be interested in helping any wastelanders nor establishing a democracy. Not the matriarchy bombers who would like to attack the Savage wastelanders. Not the meritocracy Brotherhood who look down on wastelanders and not the tribal Raiders known as the Great Khans. Worst of all, a walled City powered by a hydroelectric Dam and solar power plant with a robot army guarding them is asking for the Brotherhood of Steel to show up in mass.

Yes Man may be able to provide the information on how to build and maintain infrastructure. But who says The Courier would want to organize anything? They have no political experience. And who even says anybody would want to be organized in an independent vegas? What happens if the Courier does not handle the omertas before the Second Battle of Hoover dam? They could end up taking over the strip for themselves!