Actually in our Prophet's time, there was no bank at all but there were lot of Jewish money lenders who used to charge heavy interest/Riba to the poor people obtaining loans mainly for consumption purpose. In India the Marwari community give individual loans on high interest/Riba to the poor people. But the banks are commercial institutions spread far and wide with thousands of staff and share holders and their functions include accepting deposits, transferring funds, opening of LCs, promoting trade and business (local and international), loans to industries and commercial institutions, payment of taxes, maintaining individual and commercial accounts etc. They charge interest known as commission also. In entire Arabia, the banks are functioning accordingly. They don't indulge in over-research on a complete Deen and avoid excesses and over-acting in religious matters and rituals like us. According to an Alim, the Desi Muslims need re-conversion to true Islam as per Quran which promotes moderation as Ummath Wasth not extremism, Talibanism etc. Thanks.