Because it's never been challenged in court and the banks have not been ordered by the OFT to reduce their charges. It was on the news on Friday that a newly qualified barrister is taking his bank to court regarding these charges. If he loses he will be bankrupt and lose his job!
Isn't the barrister trying to sue the bank for damages as well? I seem to remember it saying on the news that he has been offered repayment of his charges.
We too went over our Lloyds TSB overdraft recently by �1.29 and were charged �30. I wrote to them saying I thought the charge was unreasonable. It has taken them 4 weeks to look into this but I recieved a letter today stating that it would be paid back into our account today.