I suppose an example where I might use shallow depth of field would be to subdue a distracting background and emphasize an object near the camera -- or visa versa! A broad array of tricks can always prove handy. Generally soft focus can be useful to simplify a scene to the larger forms without a lot of texture and detail. I can't say I do much of that, I'm more of a "sharpness" fan, but I guess my annual Pinhole Day excursions could qualify for soft focus.