Well, usually on overhead views, and especially in such as Google Earth/Maps, the scroll-wheel changes zoom-level. And (I think, given I don't use it much) this is what it does with the game.
Of course, for DF (unlike a lot of games, where more detailed or high-breadth of view of a map is perhaps hugely more important, it being essentially a scalable vector graphic), the very fact that the zoom-function is not so much used (by me, leastwise) means that it could be farmed off to some other control process, because what a user really wants at his/her hands is the ability to change Z-levels... But it might well be a lot more non-intuitive. Equivalent to the number of times I've gone back to the DFMA map viewer and mixed up the level-change and zoom controls on that interface, for a few moments.
But then I'm a keyboard person. And I have the Z-changing buttons easily at hand, as with every other control, and I personally find control via keyboard (scrolling around, and slicing up and down) is far more accurate than using a mouse. Ok, so there's no quick-scroll and slow-scroll ability (save for shift-cursor to move ten at a time, which is in turn also good for accuracy), compared to moving the mouse a lot/a bit, or (even with usual the 'ridge-resistance' on the scrolling wheel, while not middle button/buttin_3 ) more quickly or more slowly moving the wheel back and forth, depending on how quickly you want to ascend/descend.
DF's environment isn't a continuum, but is split into discrete blocks in all directions. As such a multi-tap is logically aligned to the same number of multi-moves in the given direction or Z-shift. I think there could be better ways to implement some things through extended mouse use, but I find it hard to be convinced that it would be a worthwhile improvement for all players (not just newbies), and that the problem with newbies-being-stuck couldn't be solved just with something more explicit (or a 'learning mode'/guided example level), once the game has settled down enough to allow it to not be a developer-diversion that has to be diverted into again and again when some later (possibly massive) UI overhauls happen anyway...
So, not sure where I went with all that. I can see where you're going, all the while with me being a stick-in-the-mud keyboard user. I think the community really has to take the lead with more (and perhaps more refined) hints and tips being available from the usual resources, and reacting quickly to all those changes Toady will bring about. This solves the "I don't know how to do this" situations, leaving us the interface complaints of "there is no way to (simply) do this" kind, within which the "sort lists" sort of suggestions lie. (But beware the latter being solved in ways that further confuse the people who are still suffering from the prior complaint. Needs to be consistent.)
((Should I summarise that summary? Naw, I'm sure it's Ok... Apolos if still TL;DR;ish, though.))