If House was a member of the Enclave, they weren't listening to him, since he predicted the Nuclear Armageddon, and set things in motion to protect Vegas...but nothing else got protected, really.
That's why i suspect he rejected their offers. He realized he was smarter than the people who claimed to be running the show, so he had no intention of suborning himself to their plans...plans that were, to him, moronic. Like getting the world destroyed over an effectively obsolete resource in the name of short-term greed.
Mr. House is still somewhat of a tool. He is still a washing-board capitalist with a capital C, even in post-apocalyptic America. I question his judgement sometimes, like why would you give casinos to treacherous, pimping scumbags like the Omertas and to a group of cannibals and then act surprised when some of them want to still eat human flesh. While the people in Freeside are starving to death and that's right outside your doors.
If his plan is really to re-energize the high technology sector, he is gonna need people to help him, I doubt his robots can do automated research. So he wants to go to orbit, explore the stars and colonize on other planets. Yeah well your gonna need a lot of people helping you do that. For starters, researching terraforming. And traveling to distant galaxies isn't impossible, we could actually do it with a plasma engine. The trick is how to control that much of energy without it killing everyone on board....but then again if they can make microfusion cells, that shouldn't be a problem either, and I suspect terraforming research could be anolyzed from a G.E.C.K.
Maybe Mr. House has plans for the people of Freeside to help in this grand achievement, or maybe he just wants to be in control, let people on his way and he will do all the heavy lifting himself.
He's an oddity that one, kind of unpredictable.