Give Me The Reasons, Why Bank Are The Regulator Of The Economy?

Banks charge interest on money that they loan to people and businesses.

If the interest rate banks charge is high then the payments will be high.  High payments may discourage people from buying things.  If people are not buying things then companies don't need employees.  If people don't have jobs then they can't buy anything.  This is called a deflationary cycle.

If interest rates are low then the payments on loans will be lower and there is less incentive to save money as you won't be getting much return on it as compared to investing in the stock market.  Lower payments encourage people to buy things.  More things being purchased mean that companies must more more people to help meet the demand.  More people working means more demand for goods and services.  This is called an inflationary cycle.