I think it is due to their fear of tax evasion. Recently they simply outlawed the use of one of their high denomination notes so there were huge queues of people at banks trying to convert their savings which they keep hidden at home. Bitcoin will make it easier to hide money
This situation is not our control, India is still developing thier systems maybe they afraid descentralized currency can beatb thier monetary compensation which is also in low price to convert dollar they are only trying to rise thier economy who knows by joining bitcoin they will rise.