If the standardization ensures the quality of a commodity, why are many goods available in the market without ISI or Agmark certification?

ISI mark is a certification mark for industrial products in India. The mark certifies that a product conforms to the Indian Standard, mentioned, developed by the Bureau of Indian Standards (BIS), the national standards body of India Standardization no doubt ensures the quality of a product but it is time consuming and expensive to avail it and Millions of micro, small and medium enterprises cannot afford it. Further it is not compulsory in the case of most products in the market, it is compulsory for electrical appliance, gold etc.