Why is there too much paperwork to open a bank account?

You always need to do a lot of paperwork to open a bank account. Why? Is it because of security reason? Not really. More money is made by banks to keep their old customers, compared with to attract new customers. This causes that the banking industry is not very competitive. If banks can cooperate together, the best strategy is to keep their old customers and not to compete with each other. In order to achieve this, increasing paperwork to open an account could largely reduce the probability of a client to leave one bank to another. Moreover, because most banks will exist for almost infinitely long time, they have no reasons to cheat on each other.