Artificial scarcity is a toxic marketing tactic
Most people have a nagging desire to collect. Everyone has a different trigger, whether it be coins or games, but there’s something almost universal about wanting to own a rare or unique item that you care about. It’s a major foundation for things like collectible card games and gacha games, where the “fun” is in paying for a chance to get that one character or card you need. It’s a psychological smoothie of OCD, gambling, and FOMO tactics that’s incredibly effective.