This history of gamification within games was more interesting than I expected. These are the game-y things like experience points, levels, and achievements that are often used to make non-games more fun or addictive.
The article is mostly judgement-free, but does include some criticism of the effect these ideas have had on games:
This is really the heart of why I think gamification harms player agency: gamification kills curiosity. If you don’t get any points, items, or achievements for the thing, the thing doesn’t matter. When the whole game is built around extrinsic rewards, you lose the player’s intrinsic motivation along the way. There’s simply no room for explorative curiosity in such loops. It becomes a “content treadmill” for both players and the developers.