What is need of bar code in every product?

Most stores have electronic point of sale (ePOS) systems which enable them to keep track of their sales and stocks and to reorder products by scanning the barcode. Most retailers refuse to accept products which are not barcoded. In addition, many distributors make use of barcodes in their warehouse systems. Retail products sold in USA and Canada feature a UPC Barcode while products sold in other parts of the world feature an EAN Barcode. The exceptions to this rule are: books, magazines, greeting cards, and prescription drugs.