Games that have relatively short run cycles and are still the “complete game” each cycle. Tetris, solitaire, minesweeper are the OGs of this but bullet heavens (aka swarm survivor), and rogue-like/lite games can have this life cycle too.
The primary reason IMO is that you can feel accomplished and satisfied with the gameplay and the story more or less isn’t important. This allows you to pick it up at anytime down the road, play it, feel accomplished, and don’t need to recall story elements. The time sink required for these games also makes it important due to the fact you can squeeze them into your schedule if you only have 1 hour, or in some cases even 1/2 an hour. The loss for abandoning midway is also inconsequential.