Never happened to me, and my family's comprised of night owls. All we stay at are the casino hotels: Atlantis, Peppermill, Sands, Circus Circus, etc. And I've never seen anyone get hassled either. I think it must be a Vegas thing.
I think you are right. There shouldn't be any problem in Reno. The main hotel I saw a problem at was in Las Vegas at the Hard Rock Hotel. That one stands out in my mind more. I remember leaving my card in the room and having trouble getting to the room when I stayed there. I never will stay there again. I think Reno is more laid back.