Really it makes great sense to me. The casinos are a world of their own. Hardly any Las Vegas natives go there. Honestly, given my brief time spent with someone actually from Las Vegas, I'd say the invisible wall between the Strip and the rest of the city is probably as good a deterrent as many international borders.

Also, there's a chance your stats are being thrown off by the fact that Las Vegas the city doesn't have very many world-class casinos. All the popular areas are actually in unincorporated Clark county, in an unincorporated community known as Paradise, NV. Make sure you include those.