I use wider lenses when I want a wider angle of view. I want a wider angle of view when I want to take pictures in which I feel the wider angle of view would be beneficial, for any of a variety of reasons.
I do it to increase how much of the background appears in the picture, while keeping a foreground subject the same size, meaning that I move closer to the foreground subject. I do it sometimes simply to increase the angle of view while keeping my location the same. I do it when I am shooting without looking through the camera, to allow myself to shoot from perspectives from which I cannot look through the camera and still get the shot, and/or to snap pictures at times at which I cannot shoot if I take the time to look through the camera, to allow myself to get reasonably sharp pictures via less-than-accurate pre focusing and depth of field. I do it sometimes to allow myself to move close enough to significantly warp a subject's appearance, while still capturing the subject within the frame.
I do all of this regardless of format, except inasmuch the format dictates subject matter. I do not as often, for instance, zone focus medium format cameras, or otherwise shoot them sloppily and haphazardly, as I do small format, since I usually choose to use a small format camera to shoot subject matter with which I find these methods of shooting to be helpful. Like you, I find myself using wider lenses less often than normal lenses, though, as I said, this is pretty much across the board, and has more to do with subject matter than it has to do directly with format. In every format, my most-used lenses are long or normal lenses. I find them easier and more "natural" to compose with, and to be better tools with which to create images that I consider "strong," "direct," and "graphic." Using wider lenses is much harder for me, though I do certainly make use of them. I find them to be excellent tools for literal representation, for one thing. They capture a lot of information, though, as I said, arranging it in a palatable fashion is harder and less natural for me than it is with normal and long lenses. When I do, however, I find myself rarely going wider than the equivalent of a 28mm lens on small format, unless necessary for some reason.
