It's not fair that only the banks are able to increase the money supply

The banking system relies on the Government to prevent insolvency.

Bank credit is valuable, to people, only because it is recognised by the Government and can then be used for tax payments. Without the Government people would not value either bank deposits or cash. The banks are existing and have not collapsed only because of the Government, and especially because of deposit insurance. Without the Government they would not be solvent.