Why play nethack?

One reason. It's hard.

It's not hard like; Aw man! This game is going to take more than 8 hours to beat, I'm going to have to stay up late doing my algebra homework! or hard like; Man, this guy's hard, I'm gonna hit gamefaqs for some tips on how to beat him!

It's hard like; I don't get it, I started a new game, took a step, fell into a pit, climbed out, tripped a rolling boulder trap, and died. What kind of game is this?

When you play a game, you expect it to be somewhat difficult. You expect to be challenged.

When you play a game, you don't expect it to be impossible or even near impossible. If the game seems to play unfairly or seems to cheat, you'll lose interest. You're still playing a game, you want to have fun.

When you play nethack you can expect to be mercilessly killed at any opportunity. The random number generator (Random Nethack God) will roll in your favor from time to time, but it's not there to give you an easy time, it's there to challenge you. You get one life to live. There are no checkpoints to go back to. You can save and exit the game, but once you return you cannot reuse that saved game. This isn't a game you play for days or weeks or even months in some cases. You can play this game for years without beating it.

To make things worse, (or better) the Random Nethack God comes armed with quite a few methods of killing you instantly. This means that your character, no matter what level or how far in the game, can die instantly if you're not careful. Most of these methods can be defeated once you have the proper equipment (equipment you hopefully can find), but many remain that you can only decrease the likelyhood of their effect on you.

The RNG isn't trying to make things difficult for you.
The RNG isn't trying to challenge you.
The RNG is trying to KILL you.

You might die of starvation. You could randomly step on a level teleport trap and be sent to hell. You might fall into a pit with poisoned spikes. A cockatrice could touch you. A swarm of killer bees could encircle you. A horde of fire ants could attack you. Even a relatively harmless gnome could be wielding a wand of death. Any number of things could happen (and probably will) that would result in your death.

The only way to cheat is to enter wizard mode where you get infinite lives and your score doesn't count. Even in that mode, it's possible to get yourself in a position where you cannot win.

Nethack has been developed for longer than any game on the market. The Dev team is constantly tweaking things to make the in-game reactions more realistic.

I play this game because it's hard. It's merciless. It's unforgiving. It demands perfection.

Don't believe me? Try it. (Just read the guidebook first)