It was as obvious 300 years ago as it is today:
“Though the principles of the banking trade may appear somewhat abstruse, the practice is capable of being reduced to strict rules. To depart upon any occasion from those rules, in consequence of some flattering speculation of extraordinary gain, is almost always extremely dangerous and frequently fatal to the banking company which attempts it.”
-Adam Smith, An Inquiry into the Nature and Causes of the Wealth of Nations, PART III. Of the Expense of public Works and public Institutions, ARTICLE I.—Of the public Works and Institutions for facilitating the Commerce of the Society.
Hat tip Lee