The games I have encountered (e.g. SimCity 4, Tropico 3) were usually designed in such a way that you wouldn't want to rely on the keyboard input as the game was clearly designed for mouse input.
In SC4 moving your mouse where you want a Residential zone and pressing the hot-key (Q,W or E) and dragging out a zone is slightly faster than clicking the menu icon, moving to where you want the zone and dragging it out. But it's not like the difference is enough to make either better than the other. But both are there so you can use which ever you're most comfortable with.
As for keyboard only, well that would be a bad idea, and that's the issue really. DF is a management game like Sim City or Dungeon Keeper and those games use the mouse (with hot-key support) for a reason, pointing devices are just better suited to that sort of task. Just like you play a flight sim with a joystick, a driving game with a wheel and an FPS with mouse & keyboard (or analogue game pad) you play management games with the mouse; best tool for the job.
Of course there are going to be players who want DF's interface to stay the same or at least similar to what it is now. I'm sure a lot of people were attracted to DF from rogue-likes and their interfaces. But DF isn't a rogue-like in any sense (it didn't even support text until Baughn added it recently), well, I suppose you could call adventure mode a rogue-like-like but the main part of the game is Dwarf Mode and that's more like the other management games already mentioned, and by those standards it has the worst interface of any management game I've ever played.
I don't know how difficult it would be to redesign the interface now, but it would definitely be worth while. It's 15, 27 and 33 on the Eternal Voting, not to mention 7, 8, 12, 26, 32, 36, 47, 50, 52, 57, 59, 67, 70, 88, 94, 96, 97 and possibly others that are in some way related to improving the interface. So the Eternal Voting and suggestion threads like this which discuss improving the interface show people do want a better interface.
I really like some of the ideas in this thread and as has been mentioned: improving the interface doesn't mean you can't keep the hot-keys or the menu with hot-key listing and it could probably be done in steps, organising it better at the game screen level and moving onto various menus such as military and trade one at a time.
tl;dr – The current interface is pretty terrible; but I play the game in spite of it. Improving it would make a huge difference and make the game more fun to play.