There are three broad benefits to regulation of a financial system.
Firstly, avoidance of negative externalities, often the societal costs of these outweighs the private cost and prevention is possible when a regulator is function well and doing their job correctly. They do this by preventing excesses, by promoting conservative risk management in the financial sector and helping to maintain confidence by ensuring (for instance) that a liquidity shortfall in one institution doesn’t spill over into others (i.e. avoiding multiple bank runs which take down well functioning solvent banks in their wake) resulting in a widespread credit crunch.
Secondly, to set solvency and reserve requirements for banks, at times there are significant asymmetries in information within the consumer/institution relationship, or worse still, information gaps (where both institution and consumer don’t have full information – as happened in the sub-prime loan market in the USA), when nobody can determine the quality and reliability of a financial product a strong regulatory environment will ensure that banks are in a position in which they can …