There are many reasons that make Las Vegas ideal. The major one it is more affordable. Air fare, entertainment, food, lodging, etc. etc.. Also saves a bundle on transport for SOE set up as their HQ is in the nieghborhood. It would easily cost twice as much, at least, in any other city that could host it. Air fares are probably cheaper to Vegas than your closest big city. Usually people who want it some place else are hoping it's in their city. That's nice for them, but the rest of the country pays a whole bunch more compared to Vegas. Oh yeah I live in Vegas 
Sabaticus