At this stage of development, any tutorial would be laughably unhelpful at best, and a development crippler at worst. Consider, every time the game changes significantly, the tutorial must also be changed to reflect that, or else become increasingly inaccurate. Keeping the tutorial updated could cost Toady a lot of extra time he could be using to advance the game instead.
I don't believe Toady's goal is to get as many players as possible passionately addicted. He's making something he loves, turning his fantasy into a reality, and he's graciously invited us to explore it while it's still in the embryonic stages. Dwarf Fortress is not for everyone; it's for Toady, and people who like some of the same things he likes.
I think the opaque user interface reflects the game well. In fact, it can serve as a useful test of character. If you can get into the game, you're probably the type to stick around. If you stall at the entry gate, you probably wouldn't enjoy what's behind it, anyway.
The kind of player most likely to appreciate Dwarf Fortress -- the diligent madman who drains the ocean if it leaks into his fortress, engineers a way to dispose of an un-killable titan, hangs a floating fortress from sky hooks, or breaches the forsaken underworld, evicts its denizens and colonizes it -- is the same kind of player who is likely to soldier on through the indecipherable user interface, scale the learning cliff, and ruin fortress after experimental fortress until he groks the game and makes it his own.
The kind of player that needs their hand held, and guidance, the player who wants friendly, simple fun: is he really likely to enjoy it when an enemy titan shows up that has no blood to bleed out, can't be beheaded or bisected because its body is amorphous, has skin harder than the hardest weapons-grade metal he can produce, can swim and breathe underwater, and just getting near it causes dwarfs to rot to death in minutes? You can kill those brutes, but it isn't easy or intuitive. You can capture them and use them as guard beasts, too, but it takes a special kind of crazy to do that. Of course, if you handle them poorly, they can and will destroy everything you love, and you'll get no help but what you provide yourself.