Why are AI researchers so obsessed with games?

In the video game, two teams of five players are placed at opposite ends of a square arena, and fight past each other using melee and spells to destroy their opponent's base. For the researcher's software to win against the pros, it would be like a robot learning to dunk on Michael Jordan. Games are an easy way for those of us without PhDs to understand how far AI research has come: When put in complex situations, can an AI beat humans? We understand what it meant for IBM's DeepBlue to beat Garry Kasparov in chess, and DeepMind's AlphaGo beating Lee Sedol in Go--decades of human practice and skill were defeated by mechanical computation. Outside of those publicized matches, AI researchers have worked for decades to build AI agents that are superhuman at playing Atari games, checkers, and even Super Smash Bros.