Nethacks like most traditional roguelike is amongst these games I like to call checklist tickers, which is to say with a moderate amount of luck, if you plod through the required amount of trivia and perfectly follow the winning moves checklist you should succeed. It kind of ruins the fun for me - playing feels more like a chore than an actual game - but it seems really enjoyable to some.
I enjoy games like this (and also other genres, like city sims or turn-based strategy games) because I enjoy seeing what happens. It's a process of discovery and interaction.
In the case of NetHack, though, it's mostly about how much hilarious stupid stuff happens, like the time I started a dungeon, took my first step, and my kitten triggered a boulder trap and killed my instantly. Thanks, kitten.
