The Sebi panel also intends to ensure that bitcoins, its derivatives, or any other cryptocurrency are not being used as a medium for funding illegal activities and no entity is able to divert black money through the virtual currency market.
They have to be able to get the money into an exchange first, for which you need a bank account in the country. I think the RBI and the IT Dept. are already overzealous in monitoring bank accounts after demonitization.
As for being used as a medium for funding of illegal activities, im not sure how that can be stopped until btc is officially recognized and exchanges are regulated even more and in a different way than they are now.