Why 'Vernacular' instead of Bengali or Bangla?

As Always, Mr Mohammad Badrul Ahsan's write-up on the former president is adroit and readable, whether one agrees with the inherent political message or not. However, I have serious reservation about the use of the term 'vernacular daily'. Not only Mr Ahsan, but The Daily Star (as also some other English newspapers in Bangladesh) has made it an occasional habit to refer to the Bengali language as 'vernacular'. Can't formal ideas be communicated through the Bengali language? Or is it too difficult to type words like 'Bengali' or 'Bangla'? This word 'vernacular' is disparaging.
Akhtar Husain Khan
Dhaka