Financial institutions (banks) are responsible in handling financial issues, records, accounts and income of individuals, companies, churches and organizations. They respond promptly according to your demands on your accounts, they also have zero tolerance for fraud and are very security conscious, security intelligence and anti financial crime expertise but they've policies of not collecting dime from customers accounts yet banks are most wealthiest institutions on earth.
When we deposit money in the bank, the bank pays us a certain amount of interest based on our deposit. Now we may have a question why the bank is paying us interest. After we deposit money in the bank, the bank doesn't keep that money, they invest that money in different places and they earn profit in different ways by using your deposited money and they give us some part of that profit. Most of the bank's income comes from providing loans to customers.