There are probably two reasons -
Firstly, India does not require a mattress manufacturer to adhere to any sort of certifications. Sunday mattresses adheres to these certifications on a voluntary basis so that we sell the highest quality mattress that complies to global standards to Indian customers. We also want to provide transparency to our customers, instead of making baseless sweeping statements such as "best mattress in India"
Secondly, there will be a 20-30% increase in cost of production, if one were to adhere to these certifications. Most of the quality standards are very stringent that call upon the manufacturers to use the highest quality raw materials and high quality machinery. There is a significant amount of initial investment and ongoing costs to produce mattress that meet such high quality standards and most brands refrain from making such a basic investment.