Banks live at the expense of funds invested in storage, while they increase this amount several times and give as a percentage to the borrower. Moreover, the borrower receives a very small part of the amount that the Bank earned on his money by issuing loans. also, banks earn doing currency exchange, insurance, sale of precious metals. These are not all ways of earning banks.
You are right. I have a friend who is a bank manager. He told me that the head office has given him a task for new accounts. A manger will show his performance by increasing the number of account holders. The more the accounts the more the money they collect. At the end of every year banks calculate their overall performance of the year and announces the bank with highest holdings as number one.