They're not the hardest problems we have, they are just very nice benchmark tools because by definition they already run on a computer and you can fairly easily

They're not the hardest problems we have, they are just very nice benchmark tools because by definition they already run on a computer and you can fairly easily interface an AI with them. There's probably also a distorting factor in that all the AI research into stock market and military applications probably doesn't get published, so it seems like video game AIs are a much larger percentage of research than it actually is.