Why tax the saving accounts?

Decreased interest rates in banks has made saving accounts more attractive to the masses. Many middle class and lower middle class families even rely on saving accounts to sustain their livelihood. 

However, the government is taxing these accounts in growing amounts, and over the last 3 years, revenue from taxing saving accounts has increased three-fold.

How is this taxation affecting the account holders?

How feasible is this form of taxation? In Straight from Star Newsroom, Ahsan Habib discusses taxation of saving accounts with The Daily Star business editor Sohel Parvez.