You can't take much off of a 4' wide porch and have a porch left. With that porch you can get out of the rain when going inside the coop instead of getting soaked as you are opening or closing the door, especially if your hands are full. With that porch to keep rain and snow out, you can open up a big area up at the top of the porch/storage area wall to get great high ventilation. There are practical reasons to have a porch. A big function may be appearance, it can make the coop more attractive though plenty of coops without porches are really cute. There is nothing wrong with attractive, it can be important to some people. If you have neighbors worried about property values an attractive coop can soothe some nerves.