Why a single factory can't make all the size/type of tiles?
Most of the factories have either 1 or 2 production lines. At a time only one size can be produced on 1 line. If a factory wants to produce a different size it needs to changeover which generally doesn't happen more then twice a month. So every month a factory with a single production line can produce 2 sizes efficiently. Now about the different TYPE of product. A factory that makes ceramic wall tiles can't make vitrified tiles in the same setup due to the difference in body preparation & temperature. So most of the big groups have separate factories for different TYPES of tiles like double charge, glazed porcelain, ceramic wall tiles, etc.