Most stores are built on a platform that makes launching easy and indexing messy. Shopify, WooCommerce, Magento and similar systems generate collection pages, tag pages, paginated lists, variant URLs and internal search results by default. Each of those can end up in the index, competing with the one page you actually want Google to show for a phrase like "linen duvet cover queen".
Meanwhile the pages that matter often have almost nothing to say. A category page with a heading, a long grid of product tiles and no text gives a search engine little reason to prefer it over a retailer that explains sizes, materials and care. Product descriptions pasted from a supplier appear word for word on many other shops, so none of them earns a clear advantage.
Shopping results changed the page, not the goal
Product queries now show free listings, image carousels, merchant panels and comparison blocks next to classic blue links. Your structured data, your Merchant Center feed and the quality of your product pages all feed those surfaces. Ecommerce SEO treats them as one system instead of separate chores handed to different people.