Sorry, what do you mean?
Basically, the historical origins of different bank regulations are quite complicated and also differ from place to place, and they were often put in place by (political) coalitions of people who already had not one single motivation but a whole spectrum of them.
And then in addition to historical reasons, you also need to ask why things are still in place. Inertia is one answer, but it's not the only one.
To understand the regulatory framework for banks, the best place to start is the BIS and Basel III. https://www.bis.org/committees/bcbs/standards Generally speaking, international banks follow Basel III in addition to their domestic regulators’ capital requirements (which are probably also derived from Basel III, but have differences just to make things tedious).
Sorry, what do you mean?
-- think that's referring to bank deposit insurance schemes...