[alkonaut]

A person being a customer of a bank means the bank has first access to that persons business when they need mortgages, other loans, home insurance, buying funds for retirement savings etc.

I suppse where bank accounts are free including services like ATM that might be an indication that banks compete for all customers - which might ni turn be an indication that all customers are reasonably likely to buy financial products such as taking loans or savings products in the future.