Early last month, many rich people in Greek began to withdraw money from banks, for they are afraid of these things happen, however, it happens now. Government can't do anything worse than forcing people leave money to save economy.
Bank holiday given in Greece to hold money in bank itself,to overcome with the economy growth. 
Greeks have been withdrawing billions of euros from their savings accounts in recent weeks which effect the economic growth.
Because in the absence of any increase in this so called Emergency Liquidity Assistance, the banks had no way to supply cash to Greek depositors who have been anxiously withdrawing their savings.