Indeed-- It was pisskop that said "then dont play"...
I was approaching more from the intellectual side of the discussion; Kinda like how the challenge presented by a tall mountain, is "because it is there". I was pointing out incrementally taller mountains, with increasingly treacherous cliffs.
As for why you would want to do any of them? Each layer of difficulty presented imposes a handicap that has wide reaching effects on how you CAN play. There are basically limitless ways to play dwarf fortress. Boredom happens when you have come up with a working formula that works basically 100% of the time. You are bored because you dont really even have to play. The formula works, you could program a computer program to simulate your input, and the game would literally run itself. Boring.
However, like the mountain, looming overhead-- the very existence of such handicaps presents a challenge, because it forces you to change your play style paradigm. It forces you to try new things that you would previously not have considered ever trying. It forces you to grow in different directions in your understanding of the game and its mechanics.
It isn't so much that I have to create some convoluted and tortured RP backstory-- In fact, the premise here was that you wanted actual challenges, which are *NOT* roleplay based. This is mechanics, and adaptive playstyle based.
You are limiting yourself and your ability to try new and crazy ideas (which may prove useful or insightful if you ever play a succession fortress and get caught up in a seriously screwed up situation where your predecessor went on a rampage and destroyed all the axes and picks in your fortress, and now you are well and truly screwed---- (or are you?
)) all because "There's no way that would ever conceivably happen, and because I assert this blandly, I just cant commit to trying."
For any of the issues I mentioned, there could be situations presented by a succession fortress where that exact symptom is being manifest--
No food: On a glacier, some dumbass destroyed all the picks in the atom smasher, animals have already eaten all the grass (It does not grow back in certain biomes!), and there are no longer any trees to cut, and no longer any bushes to pick.
This places you at the mercy of the carivans, even if only for one yearly cycle. Being able to devise workable solutions to these problems, instead of just abandoning, tests your mettle as a player.
Challenges like these are artificial, to artificially and forcefully MAKE you grow.
That's why you do them. The challenge is THERE. Like the mountain.