Other reasons to consider:
* Fortress placement. Hunting down the right location for your fortress is fun, and wouldn't be the same if one just randomly generated a patch of terrain to build on or picked from a list at random.
* Immersion. It ties your fortress into a living, breathing world, rather than just being a monolithic construction with only artificial, handwaved context.
* Adventure mode. DF is not just about the fortresses. But because they are part of a wider world, you can visit them as an adventurer and lead expeditions to reclaim them, too. Which is just cool.
* Stories. More or less the point of this project- merging the gameplay of fantasy and strategy games with the story-generating potential of The Sims. All the background the game gives you is there to be a springboard for you to colour the world with your own imagination, and make up your own narratives to give what happens in the game more personal meaning. Eventually, to have fully-fleshed narratives more or less write themselves, while you observe or intervene as desired.
Tell me that a game of Dungeon Keeper where all your monsters have their own personalities, histories, loves and hates- or a game of Sims where all your sims are four-foot axe-weilding alcoholics with seige engines and you can rig the buildings to self-destruct- isn't awesome.
EDIT: Now now, Ioric. No need to chastise people for asking honest questions.