Radiator repair, and more reading
The first reason is speed. Chains reduce the amount of time you spend waiting for a repair to be done because they can afford to have larger inventories of parts on hand, meaning you and the mechanics don't waste time waiting for parts to come in. Chains also have more employees than all but the very largest independent shops, so they have the staff on hand to a two man car repair easily and to speed up repairs by adding more mechanics if the job can go faster with more hands. An assurance of quality is the second reason. Chains hire only licensed and certified mechanics.