I disagree... New Vegas was thriving before the NCR found it, and there's plenty of people outside of the NCR in the Wasteland.
This isn’t a matter of opinion; it is a matter of facts. Mr. House only re-built the pre-war casinos in the Strip after he detected the NCR scouts in the area. Before that New Vegas was nothing but an empty city inhabited by groups of tribals.
If you look at the other powers around New Vegas, you will realize that Mr. House doesn’t really have any choice in trading partners. To the east there is Caesar’s Legion from Arizona, which clearly wants nothing that New Vegas have to offer. To the North East there is the city of New Canaan in Utah. although it is rich and prosperous, the city is rule by a Mormon theocracy, which is highly unlikely to bring lots of tourism to New Vegas, also, the city is too far away from New Vegas for them to have strong economic ties. This leaves the NCR to the west to be the only economic power that can make a difference, too bad Mr. House just basicly declared war on them... oops! :mellow:
Also, Hoover Dam wasn’t generating any electricity before the NCR engineers repaired it (it was merely in ‘an operational status’), the only reason the dam still functions is because NCR engineers are working around the clock to keep it working. Without the NCR engineers, the dam will not stay working for long. Mr. House might be able to train his own engineers, but that will take him years. By that time New Vegas' economy would have totally fallen apart without the trade and tourism from the NCR.