The reason is bigger banks basically don't make any money off low balance accounts. Interest spread earnings are minimal and the Durbin Amendment (2010) basica

The reason is bigger banks basically don't make any money off low balance accounts. Interest spread earnings are minimal and the Durbin Amendment (2010) basically killed debit card interchange as a revenue stream for banks with over $10b on the balance sheet. Smaller banks and credit unions can still make a good amount of money off uncapped debit card interchange, so they do offer free accounts.