@Gaurav Rai
Successive Indian governments have valued diplomatic freedom and if we join NATO we lose that completely.
If we join NATO our foreign policy will not be dictated from the Rashtrapati Bhavan but from Brussels.
NATO was built for one purpose: to deter the USSR and now Russia. Countries joining the alliance submitted to the clauses because each country faced an existential threat either directly from the USSR or from its communist ideology.
The collapse of the USSR has pretty much made NATO redundant since the the driving force keeping members together is now gone. Just look at the trouble Turkey is facing trying to deepen relations with Russia and China with NATO holding it back.
The alliance system that Bismarck pioneered no longer works today. The global economy is too interconnected and multilateral-ism is the way forward. Take advantage of both sides for weapons and investments.
Besides this a few other points which may have been mentioned:
1. India is not in the Atlantic.
2. We do not face any threat from Russia.
3. We are already joining the Shanghai Cooperation Organization (SCO) which is seen as a rival to NATO.
4. Joining NATO, SEATO or CENTO will cut us off from Chinese Chinese and AIIB investments which can be to the tune of 75 billion $.