Why should people have multiple identities?

People should multiple identities because this helps them to stay together. For
example in India, people think that-they are Indian as well as Tamilian, Punjabi or Haryanvi. In this way, their national identity l.e., Indian comes first and the other identity based on their state or language becomes complimentary to the first identity. This has been proved during the wars with Pakistan or disasters like Tsunami when people were united to face such crises.