Unpredictable or random rewards are more addictive than a predictable schedule.
"Random loot chests are obtained from getting 20 stars, which are earned after beating levels."
"The game has several "gacha" mechanics, such as chests and wheels, which give completely random rewards, mostly skewing towards lackluster ones."
"A dungeon crawler where loot is randomized to a degree and most loot is not retained between runs. This encourages doing repeated runs in pursuit of specific items rather than exiting the game."
"When you complete a daily mission, you can see the possible pool of loot, but it is randomized within it."
"There are in-game chests that give a inconsistent number of specific valuable resources."
"The game will help you out a lot and making you feel good then the next time you have to pay to get that same reward"