Why do people not just keep everything in Govt bonds, Tbills instead of in a bank account?

As the title suggests, I'm a little curious why do people keep significant money in their bank account. The other day I was talking with a friend who had over 15 lakh in his bank account apart from other investments. Why not just keep all of it in Govt and treasury bills or liquid funds? People talking about needing liquidity, liquid mutual funds allow you to redeem funds instantly upto a certain amount, and the remaining the early next day.