That's true. However, what's also not mentioned is that there isn't much preventing the counterfeiting of the current notes. See,

http://greatgameindia.com/de-la-rue-blacklisted-company-paki...

http://greatgameindia.com/secret-world-indian-currency-print...

http://webcache.googleusercontent.com/search?q=cache:FLhDdjQ...

(Take conspiracies with a hint of salt; the cited links seem rather solid).