For as long as there have been Magic: The Gathering tournaments there have been tournament judges. An official role during official matches since the formation of Wizards of the Coast's Duelists' Convocation International (DCI) for overseeing officially-sanctioned WotC/DCI events, judges get the mostly thankless task of tracking players' win/loss records, deciding on rules during matches, and making things are being run "by the book."
While WotC has, in recent years, changed their relationship with MTG judges thanks (in part) to a 2016 lawsuit and has all but transferred responsibility to a third party entity called the Judge Academy, at least one tradition remains quite popular: compensating judges for their service with special judge-exclusive promotional cards.
Before 1998 judges could get anything for their service: a handshake, packs of cards, maybe some money, store credit, validation of doing a good job - there was nothing set in stone. In the late 1990s, though, judges began to go over and above what was expected with judges doing everything from learning the rules by heart to coming up with fair compromises that still hold in Magic to this day. It was also in 1998 that a few of the cards had some alternative artwork and, to make the most out of it new cards were made just for them, got the special foil treatment.
Judges responded well to getting a little something extra for their time, and soon some of the rarer cards had some alt artwork specially made for these judge gift cards. Magic also began having more fun with them, such as the judge promo Elesh Norn featuring Phyrexian language type and Crucible of Worlds being available in the old brown-colored artifact card frame. And it wasn't just for simple judging either any more - some cards came out for judges simply because they hit new number of judges milestones. And since they're rare cards AND foils, they also fetch a fair amount on the open market.
Even after the aforementioned 2016 lawsuit that brought around better compensation and treatment for judges and the judge process then being streamlined some three years later, judge cards have been as strong as ever. Since 1998 nearly 150 special judge cards have been made, with ten alone coming out in 2020 including Gamble, Enlightened Tutor, Spellseeker, and an extremely creepy Demonic Tutor.
Despite COVID-19 and tournaments pumping the brakes for awhile, judge cards are expected to be coming out for some time to come.