Well, the rooms are free to locals. No, not you daily Californians. We still have to pay about $30. Primm has been an underrated value, but it's always been my experience that it's tough to convince a Californian to actually stay there. Even if it's only for a day. Most of the time, the thought is, "If we have come this far, why not go all of the way?" And there is some truth to that.
Still, they should try to give Southern Californians some free nights and see if they can't build up some loyalty.