You forget that the three families were savage tribesmen before Mr. House got them on his side, now they are all rich business men making thousands of Caps a day, if the entire Mojave were on his side, they, like the three families would prosper too. Mr. House could probably make Freeside and westside prosper too but the arrival of the NCR and the legion have limited his sphere of influence to the strip, if he tried to get them on his side then the NCR and legion might see it as a threat and take him out early.
and if Mr. House really is so bad at running things then how did he create the largest robotics/computer corporation in probably the entire world even after he was cheated out of inheritance? If he was so bad then how did he save Vegas? If he was so bad how did he manage to recruit the three families when they were previously aggressive tribes people? If he was so bad how did he manage to kick the Great Khans (a large tough tribe that can terrorize the NCR) from the strip with a handful of Mk I securitrons and some tribesmen? If Mr. House is really so bad at running things then how did he do all this?
Neither house or his securitrons can run the casinos so he obviously needed a group of people who were capable of doing it. He did make savages rich but he didn't do it for the greater good. He was thinking what was best for Vegas not "how can I save these tribes from the violent wasteland".Previously aggressive tribes? Lets see,The Omertas want to take over the strip&they cover up murders,The White Glove wants to bring back cannibalism, Benny wants to take over the strip and even Mr. house says the chairman share a "tribal affinity" so if Benny did take over I bet they would support him. They all are
still savages. But let's say Mr. house is the best choice for the Mojave. Do you really think people should live under his rule
forever? Even if his rule is good should one have power for eternity?
Having good or bad Karma for killing someone doesn't make the game "Good" vs "Evil." I agree with you that Karma was not needed for New Vegas. I disagree that Karma was done better in Fallout 3. In Fallout Karma acts as the games "reputation system." So this is where Karma worked the best. Fallout 2 was when the reputation system came in, but Karma still worked really well with it. Fallout 3 just had Karma, but Karma didn't affect how the game world saw you. It was completely pointless. New Vegas has the Reputation System which governs how the game world sees you. Karma took a backseat. I rather have the Reputation System. Karma is no longer needed.
Fallout 3s did affect how the world reacted to you.
-Companions wouldn't follow you if you weren't like them.
-Three dog mentions your actions, right or wrong.
-Talon and regulators.
-Unique Dialogue (ex.I remember a kid telling me they shouldn't talk to me because I'm a bad person)
-The ending
I think it could've been more to it than just that but this was their first fallout title and they were simply experimenting on new things. The reputation system is nice but why not have both? I don't think the two would really conflict each other and both seem to have benefits and consequences.