Cropping a photograph is a useful post-processing technique that can be used when a photograph has a distracting background, foreground, or perhaps artifacts are in the photograph that might otherwise distract the viewer. Cropping is often used in street photography as the photographer will not have time to capture the frame perfectly, and errors on the side of too much in the frame instead of cropping out a subject, or important detail.
This image has a noisy background with stairs, a house, and other things that distract the viewer. If a better DOF had been achieved, the background would be blurred and perhaps a crop not needed quite as bad.
We have created a much tigher crop around the contruction workers. There is no longer a distracting background that draws the viewers attention away from the subjects in the image.
For more information on this topic, also see the following TFTTF shows: