Lazy People

Why is it that some people won't shovel the sidewalk in front of their houses after it snows? Now I understand if that person is not physically able to shovel the snow. Say if you are physically disabled, or elderly, or have had surgery recently, or are dead, then I understand not being able to shovel any snow. But if they are someone who is perfectly able to shovel snow, and they won't shovel their sidewalk, then why don't they? What is worse is that some will shovel their walkway, and they will shovel out their driveway, but not they're sidewalk! What is the point in doing that for anyways if you are not going to shovel your sidewalk? I see that and it really makes me mad, because to me it says, "I can do it, but I'm to lazy to do it and don't give enough of a damn about other people to shovel my sidewalk."