With a normal or tele lens, you can easily focus on a detail and compose a few elements into a shot. With a wide angle, and especially ultra wide-angle, the camera is going to capture everything, so the image will be chaotic and full of possibly distracting details. So the pohotographer is going to have to work to try to make some order out of that chaos, and is necessarily going to have to get closer to his subject, like any wide angle photography really, so that there is somewhere for the eye to focus and not just a mess of background with no real subject.
By getting closer to the subject the shot will have a more intimate feel. Not like the photographer is a distant observer, but more part of the action. As a result the photographer is more likely to be noticed and more likely to get a reaction from his subjects, whereas with longer lenses you can often catch people unaware.
So for documentary photography, using a wide angle is going to most likely capture images of people who are quite aware of the camera, but you will get closer and more intimate with the subject, and you will also capture more of the surrounding environment with the shot.