Not going to teach people how to launder money, but one of the avenues that can be used to get a respectable transaction is to overpay from a dirty bank account to a credit card, and then the financial institution will credit into the users clean bank account which will raise less flags then a direct transfer. This is just one step in a process, and not even sure it works anymore. But many banks would rather just not deal with it.

It’s to stop money laundering