[Peku]

I don't think they were intentionally, but some people can get addicted.

One more level

Just after this boss

I think single player games now are just as addictive as they were then. Especially when you look at indie games (Shovel Knight, Death's Door etc).

The moment interaction with other players happens is when I feel a higher bump in addiction can happen. Loot boxes, seeing a cool skin etc.