I have a friend who teaches at Cornell's famous School of Hotel Administration; she has a lot of casino designer contacts. According to her, the carpets are deliberately designed to obscure and camouflage gambling chips that have fallen onto the floor. The casinos sweep up a huge number of these every night. So the carpets are just another source of revenue.
There is more at the link, including some striking photos. For the pointer I thank Arun Eamani.