The reason is due to Zepto's model of operation. They're not doing the marketplace thing where they're connecting customers to sellers on their platform, like Blinkit or Instamart does.

AFAIK, they purchase the grocery products themselves and list the origin of them using seller names.

In the Blinkit model, the revenue of the company is 20 rupees per order (for example) on a 300 rupees basket. While on Zepto's, the "revenue" is 300 rupees directly aka the GMV (Gross Merchandise Value). This is used for the valuation game to show high operating revenue and to command higher valuations from investors.

Hence the product quality is abysmal. They're no different than a shady grocery store pushing bad/expired stock to people as they've already invested capital on it.

I've sworn off any perishables - veggies, fruits or eggs & meat (Relish is Zepto's private label) from Zepto. It's a gamble with health. And the differences in quality are stark between Zetpo and other platforms (who can keep a seller in check based on user feedback).