The variation I heard was the the American Chemical Society (ACS) held their 1997 meeting in Vegas. The casinos didn't make enough money from the 13,000+ people who were there, and don't want the chemists back. Checking now, there hasn't been an ACS national meeting there since then, and the schedule, which goes up to 2019, doesn't show any future meetings there.
For what it's worth, neither does the American Statistical Association.
lol. Mine was told to me by a chemist. Did a physicist tell you the APS version? Looking at the APS calendar, they also have no upcoming meetings in Vegas.
For what it's worth, neither does the American Statistical Association.