There are a lot of possibilities with games, and different types of games work differently for different people, that's for sure. In any case, the reason I brought up the Skinner box stuff is because these techniques are used to condition a player to keep doing something even when it's not fun anymore. There comes a point where, logically speaking, there is nothing enjoyable about killing monster after monster, doing the same missions again and again, grinding, grinding, grinding until you get carpal tunnel and can't tolerate the light of sunlight anymore. This happens most obviously in MMORPGs. The developers can't keep creating new content as fast as players can get through it, so what do they do? They addict you to playing the same content over and over and over again. They do it by giving you those little psychological rewards, the popups, the XP, the gold, the random item drops. Making them collectible and adding achievements makes it even more addictive. If you put in the same amount of effort at a real job, you probably wouldn't get the same sense of achievement as you do when you level up in a game, so people end up spending more and more time at the game and less on real-life useful things.
This is how HabitRPG works. The idea of motivating you to do something that isn't fun doesn't have to apply to clicking and button-mashing. In this case, it's chores, exercise, work. But instead of the vague, long-term benefits that the real world offers, you also get the instant gratification of the XP, the gold, the random item drops. You can collect pets and mounts. You can complete quests. You get a much greater feeling of achievement from doing your housework than you would without the game. That's how it works, and I think this might be the best application of Skinner's techniques I've ever seen.