Though Bangalore is a relatively new name, it has been deeply ingrained in recent collective memory and literature. So it needs some time to change. Other cases in point, Bombay -> Mumbai. Madras -> Chennai, Calcutta -> Kolkata. While these changes have been adopted in some circles, the anglized form is still in use in many places. Especially, places and instances that have history pertaining to the past few centuries.

Also, in IT field, Bangalore symbolizes more than the city. It is a standin for the Indian IT industry and it's boom in general. It has a certain connotation and degree of recognizability that may be lost when using Bengaluru. Still with time, it too would change.