It's full of real scum-of-the-earth types. For example, a gang called the Skulz, led by Vinnie, hang out in the casino and do various illegal and quasi-legal jobs for Gizmo.
If the gamblers aren't satisfied with the casino, they can bet on the boxing match with Saul. Also, the Skum Pitt is available. Most travelers are here for relaxation. Killian Darkwater, Junktown's mayor, constantly tries to shut the casino down, but always to no avail.
There are multiple discrepancies about where Gizmo's Casino is actually located in Junktown. Killian's dialogue lines place it at the entrance, from the logic of map design it would be found at the west end of L-shaped Junktown, and from the way the exit grids are placed it is in the east.
There is a neon sign outside the casino - an otherwise rare prop in southern New California.