Common squirrel monkeys observe their Christmas present, a box full of mealworms, at the South America enclosure of the Budapest Zoo, in Budapest, Hungary, 24 December 2017. (Photo by Photo by Attila Kovacs/EPA/EFE/Rex Features/Shutterstock)

A series of Japanese good luck charms, called “Daruma”, are lined up ahead of the major national elections November 9, 2003 in Takasaki, Japan. The Daruma is said to bring exceptional good luck in all walks of life, but is used especially during election time by all candidates. People think that if they face a difficult situation, as symbolized by the doll that returns to its original position when knocked over, they will always bounce back. (Photo by Koichi Kamoshida/Getty Images)

Dance Team Rage Crew perform at BAFTA LA's 6th Annual Christmas Party and Toy Drive at Helen Keller Park on December 17, 2011 in Los Angeles, California. (Photo by Frazer Harrison/Getty Images)

A tourist has her photo taken wearing a Santa hat on Christmas Day on Bondi Beach in Sydney, Australia on December 25, 2018. (Photo by Peter Parks/AFP Photo)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

Two robotic legged squad support system (LS3) machines by the Defense Advanced Research Project Agency follow a technician during a demonstration at Joint Base Myer-Henderson Hall, Virginia, on September 10, 2012. (U.S. Marine Corps photo by Sgt. Mallory S. VanderSchans via The Atlantic)

A Guinean kid poses for a photo in Conakry, Guinea on July 23, 2021. Children, most of whom start working after a certain age to support their families, have their hair braided in different ways and decorated with colorful beads on all special days, especially on holidays, despite these difficult conditions. (Photo by Ozkan Bilgin/Anadolu Agency via Getty Images)

A fisherman with a close bond to cormorants uses the flock of birds to catch big fish in Li river in Guilin, China. The aquatic birds can be seen perching on a bamboo raft before swooping into the calm water to grasp hold of prey. (Photo by Julia Wimmerlin/Solnet News & Photo Agency)