Finished side panels are needed if the side(s) of a cabinet are exposed, and when cabinets are placed agaist a range, stove or grill.
To keep down costs of our cabinetry, finished side panels are only applied to cabinet sides that need them.
If finished side panels are not put in they leave an "unfinished look" as seen on the left hand pictures, but give a "finished" look when applied as seen in the right hand photos.
Finished side panels are not needed if the cabinet side is attached to another cabinet, is against a wall, or if the cabinet is against another structure or form that will make the cabinet side unexposed.
Finished side panels are needed on the cabinet side that is against a stove, oven or grill to prevent any combustibility issues and to prevent grease and other material getting in the grooves of the cabinet side.