Why late Indira Gandhi has not change her sur name after marrying a muslim community?

When Firoze who was a parsee and not a muslim, was wooing Indira (not 'Indra' which is a masculine name being the king of gods), her grandparents objected her marrying from a different emigre religion. M.K.Gandhi then adopted him and named him Feroze Gandhi and the marriage was consecreted under his supervision with the couple exchanging garlands made of hand-spun cotton yarn (Khaadi) and that is how Indira became Indira Gandhi, the Gandhi connection she showed off to good effect.