> as it is controlled by central banks and can be arbitrarily increased.

Its really not controlled by central banks. Its influenced, but not controlled.

When central banks "print" money, they effectively just add money to the accounts of investment banks

But investment banks are also "printing" money. Double accounting effectively uses assets to double the available pool of money. If you then sell off those loans based on those assets, then you crystallise that new money. Investment banks are inflationary.