Many great games can be completed. You beat the final boss, the game is over and you get a feeling of satisfaction. A game with an Infinite Treadmill cannot be completed and never gives you that sense of satisfaction. You can play forever, constantly leveling up and improving, but never reaching the end. This is a very common pattern seen in multiplayer online games, and many people enjoy these types of games. However, for some people this can be a dark pattern, especially when combined with Recurring Fees
or other types of In-App Purchases
People have a psychological need to complete something that they have started. This is called Endowed Progress
or the "Zeigarnik effect". The urge to complete something that can't be completed causes some people to play the game forever, even after they have become bored with the game.
Sometimes games are designed such that there is no way to complete them. You may beat an individual level, but you can play an infinite number of levels and keep earning benefits forever. For a game to fall into this category there must be some overarching progression that extends beyond individual levels. For example, a simple game of chess against the computer would not count as an Infinite Treadmill unless winning or losing an individual match had some reward or repercussion that carried over into the future matches. Many multiplayer combat games are designed like this. You can always start a new battle, and your success allows you to improve your character in future battles.
Another way that developers implement an Infinite Treadmill is by continually expanding the game and adding new content. It might be possible to complete everything in the game right now, but soon the developers will release new levels and extend the game. As long as the developers are still working on the game, new content will continually be added and the players will need to keep playing the game if they want to complete it. Nobody is saying that you have to complete it, but the Fear of Missing Out
is a strong motivation to keep playing to see what happens.
Additionally, if someone is already bored with a game and a new event is announced, the player may stick around to see if the new event rekindles their enjoyment in the game in which they have already invested
significant time and money.