>>716053773 (OP) Because you can keep challenging yourself. Higher difficulties, special seeds, using only certain types of weapons and so on. There are so many possibilities, 1000 hours of play time easily.
>>716053773 (OP) Because it gives you tons of tools that break the game, and it doesn't take that long to mine stuff. The gameplay loop is just good. It kept receiving decent QoL and balancing patches. Every phase of the game is fun in it's own way, and not one part really overstays it's welcome for too long. The bosses are cool and the combat/gearing is simple and fun.