On a related note, does that make people in (e.g.) Bangalore speak Hindi more than Kannada?

In China, the purpose-built electronics city of Shenzhen is full of migrants from other regions, so the local language is Mandarin even though the surrounding Guangdong province speaks Cantonese.

In Hyderabad which is in a neighboring state to Bangalore, most people speak both Telugu and Hindi.

Among white collar workers English is pretty common.

Not really... native Bangaloreans generally make it a point not to speak Hindi. As for people in the IT Sector, "English is the Lingua Franca" (pun intended) :)

The three states surrounding karnatake (where banglore is located) don't speak Hindi...

It does, but it's more likely if you're in one of the large cities - Mumbai, Delhi, Bangalore, Kolkata, Chennai. People move for jobs and economic opportunity. Smaller cities have fewer opportunities and thus fewer reasons for out-of-state people to move there.