No offense, but why do teachers teach English in Hindi?

I am just curious as to why. Like I get it people can understand the concepts better and stuff like that but I'm sure most of us can understand at least basic English or if the concept is too difficult to be understood by students, then yes, Hindi can be opted for. But I genuinely don't understand the logic behind using Hindi to teach even the basic stuff of English. It kinda contradicts the whole reason as to why we even have English as a part of the exam in the first place.

ETA: I'm from south. We all know and can speak atleast basic English here. That's why I assumed that's the same in North as well and asked why teachers do this. While I have no problem with learning Hindi (which is what I do coz blaming that I got no to less resources in my language is just a waste of time), I felt like why not teach atleast english in english. I feel like many won't get the pain behind this and that's completely fine.