You must be thinking 100%, of course. Well, that’s not the case. India is home to tens of hundreds of languages and ‘Hindi’ is just one of them.
Not all Indians speak Hindi. Hindi is the most popular language in Northern India and as per 2001 survey of India, 53.6% Indians speak Hindi & only 41% of Indians call Hindi their ‘mother tongue’. Rest of the Indians doesn’t know Hindi & speak other regional Indian languages which includes Bengali, Marathi, Telugu, Tamil, Gujarati, Urdu, Kannada, Odia, Malayalam, Assamese, Kashmiri, Punjabi, Sanskrit, et cetera.
So, If one is an Indian, that doesn’t mean that s/he needs to know Hindi as well, and vice versa!
Bonus Fact: India is the world’s second largest English speaking country, where about 12.5 crore people (which constitute about 10% of Indian population) speak English!