Smart regulation ensures that financial institutions can still pursue their business, but that they are appropriately protected against the biggest risks. This then safeguards the economy, consumers and the financial system itself against turbulence. Therefore, the reason we can't give banks and savings banks full rein is because of the important part they play in the economic cycle.
Smart regulation and close supervision are also desirable from the banks' and savings banks' point of view, as they prevent cost-intensive threats to their existence. There are more advantages for the sector as a whole.