Generating 74 percent of total payments related
income, current accounts (known as
DDA in the United States) are the core of
the European payments business. In 2007,
retail current accounts contributed €39 billion
in profit, mainly from interest on balances,
out of total payments-related profit
of €68 billion. Corporate accounts added
another €11 billion.

We are currently in a weird situation where banks do not have many places to invest deposits profitably.
http://www.nytimes.com/2011/10/25/business/banks-flooded-with-cash-they-cant-profitably-use.html?pag ewanted=all

But your model of how depository banks work is wrong.