Without going too deeply into the matter I just want to refer to a dissertation thesis by Dr Juha Tarkka, Advisor to the Board in the Bank of Finland, according to which this cross subsidization may be a fully rational response to prevailing conditions for three different  BIS Review 64/2009  1  reasons; the taxation treatment of “free services”, price discrimination between customers under imperfect competition, and customers' uncertainty of their service requirements.
1 This cross-subsidization may now become more difficult if interest rates remain low for a long period of time; the difference between market rates and the rate paid to transaction accounts must be narrow if market rates are close to zero, implying that attracting deposits by offering free payment services would no longer be a profitable strategy.