The problem is one of geography. Dubai is acting as a regional entrepot for the Middle East and convenient air hub between Europe and Asia. There weren't any competitors in the Middle East because everyone else was solely a failed state, rogue terrorist regime, or conservative oil barony. So they became the only player in the game within a region that needed someone to be so.
Las Vegas doesn't have that geographical advantage. The US already has many ocean and air ports that serve a vital transportation function (LA, Chicago, New York, Miami). There is no reason for anyone to stop at Las Vegas when they can fly an extra hour and reach LA which also has lots of other advantages over Las Vegas.
Las Vegas also can't offer a better business climate than anyone else in the area because everything is still in the US. In contrast, if you don't want to do business with Dubai, you're dealing with the Iranians, some corrupt monarchy, a terrorist failed state, etc. Even if you think Las Vegas could offer a better business climate than say California, there are plenty of pro-business places you can still go to in the US, all of whom have more advantages than Las Vegas.
This isn't saying that Las Vegas can't do better than it has done IOTL. It's just that opportunities are more limited because there are many other players who will absorb talent and investment who would otherwise go to Las Vegas.