Even though banks can make huge profits but it depend upon masses, It is very hard to run and maintain a bank. Most of the revenue come from the loans they give and from credit cards. But if they don't have many customers due to big rival bank. Small banks will suffer and also goes in debt.
And now after Digitization if they don't move towards it and adopt it. They will be in huge debt. Big banks can do easily as they have more money and can get easily adopted any new technology. :)