It's like saying if you can't beat them, join them. Banning bitcoin would just make people transact it hidden in the government's eyes which would make it harder for the officials to track the activity of the people. If they would just regulate it then they would know what is happening and they can have funds from it as well whereas in banning it, they wouldn't have any share from the transaction.
There is an increasing interest of bitcoin in India so if in case the Supreme Court would decide to ban it, some people may stop using it but there would be some who will continue and they will be force to go underground which would be disadvantageous to the government.