Loot boxes, mostly. Gacha games and the like pioneered it and now it's in everything. The slot-machine pull does something to people, and I'm more worried about what it does to brains that haven't completely set yet.
Fortnite doesn't have loot boxes. There's skins and dances, but you buy them all directly, there's no RNG. At least that I've found in my ~30 hours of playing the game.
It's just like golden eye, but now you've got to pay to play as odjob.
Sorry, you're right, I shouldn't have used the example of Fortnite when I personally play PUBG. And Overwatch. Both of which do. ;) My reach exceeded my grasp.
Although Fortnite doesn't have explicit lootboxes, there's certainly a related addictive effect to simply opening chests, stumbling across a Llama, etc. Have you not heard a younger player squeal 'scaaarrr'?