Two famous (great?) Indians. Both live outside India. Both travel a lot. They have been doing it for years. One is an artist and the other a scientist. It would be convenient for both to have 'western' passports. Both retain their Indian passports.
The reason they do so are so different, perhaps, defined by their chosen fields. One feels that his Indian-ness defines him. The other says that it is because he wants to criticise India – in a constructive way. He wants to participate in the debate and feels that if he does not retain his passport he loses his right to do so. The reasons are as different as their fields. To make an artificial distinction, one's decision is from the heart and the other the head.
They are Zubin Mehta and Amartya Sen. (Economics is a science too, even though an inexact one. Of course, with Quantum Theory even the exact science of Physics became inexact, a long time ago.)
Kudos - to both of them! May their tribe increase!