At least as of about 4 years ago, Harrah's Rincon was FULL of them. I spent several days there in 2015, and I was astounded by the number of druggies milling around the place. A lot of them even became friends with one another over time.
Some methy-looking chick who was my age approached me and talked to me (who I kept talking to out of amusement), and in the middle, we were interrupted by some clean-cut-looking Indian dude who quietly made a sex-for-drugs deal with her.