Vegas is hurting on its own and people wouldn't be going there no matter how many flights would be going in. I was just there and it's shocking--- you can find $5 craps tables at some of the older casinos *on the strip* and $10 craps at the bigger MGM resorts on a Friday night. That's unheard-of. Even 6 months ago you couldn't play a table game on a Friday night with less than a $15 buy-in. There's very aggressive discounting going on for shows and events, too. I would not be surprised to see some of the casinos come out with really good package deals that cost the same for air+hotel as just air, hoping that once they get you to their casino, you'll spend some money and make it worth their while, or some partnerships between select airlines and select casino chains (i.e. fly US and stay at MGM and get $500 in casino free plays).
While it is not at all convenient for me to have fewer flight options, I do not blame US or any other airline for cutting back here. People are just not going there and if airlines are all facing bankruptcy again, why fly a half-empty plane when you can cram everyone into the other routes and fly fewer, fuller planes? Again, I don't particularly care for the overfull planes but it makes business sense.