As far as I know, the only actual legal requirement is that SEPA transfers to other countries can't be more expensive than in-country bank transfers. It just happens that a lot of European countries don't generally have charges for bank transfers.
Yeah I knew it's not a legal requirement but still I thought it would lead to zero fees everywhere, because now when you need to do a lot of transfers, it makes sense to create an account in a foreign SEPA bank and then even the transfers to greek accounts would be free. Granted I don't know how much are bank transfers used in Greece (given the fee probably not to their full potential).
