Nobody had been allowed inside the Lucky 38 since before the Great War; that's where Mr. House looked over the New Vegas Strip, after all, and the CEO and founder of RobCo didn't see just anyone.
You're an exception. You've been through hell and back making your way to the Strip, and Mr. House saw this. Using one of his Securitrons, Victor, you were invited to the Lucky 38 to see Mr. House himself.
At least, his hologram. Normally, his face would be plastered across the giant screens in the penthouse, but it seemed like he managed to get his hands on holographic technology, giving him a neon green hologram of his pre-war self.
He straightened out his suit as you entered. "Ah, you've come, good. This meeting has been a long time coming, hasn't it?"