Personally, I cannot think of a reason why India was not made a nuclear-weapon state in the “NPT.”:http://www.fas.org/nuke/control/npt/text/npt2.htm
Well, except for this:
bq. For the purposes of this Treaty, a nuclear-weapon State is one which has manufactured and exploded a nuclear weapon or other nuclear explosive device prior to January 1, 1967.
Indira Gandhi “didn’t argue”:http://www.indianembassy.org/policy/Disarmament/disarm10.htm at the time that India even _wanted_ nuclear weapons:
bq. we have stated that the Government of India does not propose to manufacture nuclear weapons. This is a decision taken many years ago and is unrelated to the treaty on nonProliferation of nuclear weapons. We shall continue our efforts for nuclear disarmament because it is only through nuclear disarmament that discrimination would be eliminated and equality between nations reestablished.