There is no such thing as “official language of India”. Saying people “ought” to know your language is plain hegemony and racist. The locals also feel the same, that the people living in their region “ought” to know the local language and they have a valid reason to feel so.
I’ve just returned from a 3 country visit in Europe, each one of them spoke a different language, except for Sweden, the others didn’t speak or understand English, except for the educated class.
If you were to travel abroad similarly , would you have the same demand that they “ought” to know english ? I’m sure you would try to learn a bit of their language for survival.
FYI, I live in Bengaluru and Kannada is not my mother tongue but I’m making an attempt to learn the local language and the local culture.