Would people care to experience it if they could? I've always assumed with this (and a number of other things in life) that being a bit of a niche interest (or in this case a lot of a niche interest) in part creates the niche interest. There have been many rogue-a-likes with more modern interfaces but they have either not attracted or not managed to keep up the interest that this one has. Perhaps it is a nostalgia thing, perhaps it is a "nerd" thing; what-ever it is it works for them and their audience and changing the game to appeal to a larger audience might both fail to do so and make the existing fans wander off (and make it less enjoyable for the developers to work on: they seem to be getting quite a kick out of their baby and its current fans and don't want to lose that).
The comparison some make with minecraft on the "being a bit niche creating a niche" thing is quite fair, and this "if you were more like that you might have a much larger audience" comments perfectly valid, but minecraft's niche being an order of magnitude or few bigger might be in part due to luck (right thing, right time, critical mass didn't hit to early or too late, ...) rather than just the relative prettiness and intuitiveness.
Caveat: I've played neither Dwarf Fortress nor Minecraft, so I may not really have a clue what I'm talking about.