Still, I would imagine major e-commerce websites to add support for a langugage in the website, if the potential userbase is big enough (for example, the Apple Store does).
My knowledge of India is very limited , but it always seemed to me that the unifying language really is English (again, from a very cursory glance, Amazon, Apple and HP have Indian e-commerce stores in English).
My point is that decoupling language and location as a general feature does not make much economic sense in the vast majority of cases.
This is especially true for major e-commerce sites: think about Amazon, and the number of items being sold (millions ?). Many of those are sold only in a particular store, or have variations between a store and another: how much would it cost to translate all the articles for all the stores in x languages ?
Your browser already tells every website what language(s) you speak in the Accept-Language header, so it's not like that information isn't available.