For me it's not the casinos. The only reason why I want to visit Las Vegas very soon (maybe next year, or the year after) is to go to the Star Trek convention.
Every year I read about the happenings there, the panels, the fun, the craziness, and above all the unfettered enthusiasm for everything Star Trek and science fiction.
And every year I think: "I really need to go."
Here's an article about this year's convention. As a sidenote: Terry Farrell is an incredibly beautiful woman.