The central banks can't force anyone to deposit money in negative-interest-bearing accounts, except for relatively small reserve balances that banks can't/won't hold in cash or other short term liquid assets. Without the central banks, those daily reserve deposits would have to be held in cash, which would have a higher cost/risk than the central bank, as evidenced by banks keeping their deposits in negative-interest-rate accounts. They wouldn't do it if they had a better option. If banks were not even required to hold a fraction of their liabilities in reserve then bank runs would probably be far more common, but interest rates might be slightly higher between the busts.