How would the banking system work without interest?
Why would you ever give a stranger your hard earned money for 30 years? This means that you will be unable to buy things this period of time.
Do you know how money is made? How it multiplies as the same money is loaned out again and again?
A bank doesnt earn
The benefit of a banking system is that it empowers people, as you are saying. This is it's function, and economic growth in the community around it should be sufficient incentive, particularly since the commodity banks deal in has no real value in itself.
When you take out a loan, a bank doesn't give you it's own money. It simply adds the sum you promise to pay them to it's holdings, on an account in your name. It is one of the ways new money is added to the supply.
It really is an effective system. But adding intrest to it creates a paradox. There will be more debt than there exist money to pay it off. This has the ultimate effect that real wealth ends up in the hands of those who control the money supply, while everyone else ends up indebted to them.