Saying that the "head" has to be the CEO is taking it too far.
In most large companies, you are only aware of the behaviour of the two levels of management above you. If you see your boss or your bosses boss behave in a certain way, you will think that this behaviour is acceptable.
For example, the CEO of some bank might be very long-term, risk free, investement oriented, but if the boss of the trading desk only cares about the next paycheck and is willing to take risks to get his bonus, chances are all the traders will do whatever it takes to get good results without more than a year ahead.