It is addiction. Addiction to the adrenaline of the gameplay elements, that’s literally how games like Destiny/League/Genshin are designed. The “loot box” mystery loot rewards is literally predatory and designed to abuse the psychology of the people that play those games to keep them coming back for more.
Destiny especially revolves around loot. And you get randomized “mystery” loot. I would know, I played the first game and the second game until the Shadowkeep expansion, then I didnt buy other expansions. Because why would I? Bungie deleted stuff I paid for.