Sort of but the simple answer is taxation. If everything goes through your bank the black economy is dead.Stopping money laundering.
I paid cash in a restaurant in Manchester last month, they did not know what to do with it, just took it into the back somewhere eventually and made no attempt to check or count so we just left.
Going back to the info City have on you.
They have my name and date of birth.
My home address, e mail, home/mobile phone number, bank details including possibly credit card. I went to Porto so they even have my passport details.
They know how many children I have and how many City friends I have. The police or Inland Revenue would love that sort of info and so would a marketing company.