A young arab boy, armed with a rifle and a knife, in the Aden Protectorate near Yemen. (Photo by Richards/Fox Photos/Getty Images). February 1938

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.

In this Wednesday, January 23, 2019, an anti-government protester covers her face with a Venezuelan flag, and uses toothpaste around her eyes to help lessen the effect of tear gas, during clashes with security forces after a rally demanding the resignation of President Nicolas Maduro in Caracas, Venezuela. The head of Venezuela's opposition-run congress declared himself interim president at the rally, until new elections can be called. (Photo by Fernando Llano/AP Photo)

A labourer rides a donkey cart through a flooded street after heavy monsoon rains in Lahore on August 20, 2020. (Photo by Arif Ali/AFP Photo)

Models get their makeup backstage during the Ukrainian Fashion Week in Kiev, Ukraine, 01 September 2020. (Photo by Sergey Dolzhenko/EPA/EFE)

A girl carries sorghum stalks during the sorghum harvest season in Amran province, Yemen, October 24, 2020. (Photo by Xinhua News Agency/Rex Features/Shutterstock)

Wrestlers participate during the traditional Sindhi Malakhra wrestling in Larkana, Pakistan, 30 January 2021. A Malakhra match begins with both wrestlers tying a twisted cloth around the opponent's waist. Each one then holds onto the opponent's waistcloth and tries to throw him to the ground. (Photo by Waqar Hussein/EPA/EFE)

A child travels in a pickup truck next to a coffin in Les Cayes, Haiti, Monday, August 16, 2021. Haitians are searching for survivors and the dead in collapsed buildings following the powerful earthquake over the weekend as hospitals overflow with patients, and Tropical Depression Grace is predicted to reach Haiti Monday night. (Photo by Joseph Odelyn/AP Photo)