If you are looking for actual for games featuring survival or romantic subplots (like various Roblox "Apocalypse" experiences), these are used to unlock items, currency, or cosmetic "skins." For example, Survive the Apocalypse
Decoding the Apocalypse Lovers Code: Romance at the End of the World Apocalypse Lovers Code
It serves as a "thank you" to players who financially support the project. If you are looking for actual for games