One is multiple parallel goals. Makes it hard to stop playing, since there’s always something you just want to finish or do “quickly”.
Say you want to build a house. Chop some trees, make some walls. Oh, need glass for windows. Shovel some sand, make more furnaces, dig a room to put them in - oh, there’s a cave with shiny stuff! Quickly explore a bit. Misstep, fall, zombies, dead. You had not placed a bed yet, so gotta run. Night falls. Dodge spiders and skeletons. Trouble finding new house. There it is! Venture into the cave again to recover your lost equipment. As you come up, a creeper awaitsssss you …
Another mechanism is luck. The world is procedurally generated, and you can craft and create almost anything anywhere. Except for a few things, like spawners. I once was lucky to have two skeleton spawners right next to each other, not far from the surface. In total, I probably spent hours in later worlds to find a similar thing.
The social aspect can also support that you play the game longer or more than you actually would like. Do I lose my “friends” when I stop playing their game?
I don’t think Minecraft does these things in any way maliciously, it’s just a great game. But nevertheless, it has a couple of mechanics which can make it addictive and problematic.