Highway robbery

What makes banks and utilities companies think it's OK to charge someone money as a late payment fee/overdrawn fee? If someone doesn't pay their bill doesn't that create an assumption that they are short on cash and therefore charging a late fee means they are even less able to pay the bill?
We forgot to pay a bill with a certain telco (Foxtel. Oh, did I mention their name...?) and the next bill had a FIFTEEN dollar late payment fee. We literally misplaced the bill and it wasn't paid on time. Now, I know that these companies will defend themselves by saying there are costs involved with unpaid bills but having worked for one of these large companies I can tell you that it only involves the computer adding the charge and spitting out a letter. Surely that doesn't cost $15. Grrrrrrrrrrrrrrrrr Angry!
We are going to quit once our contract is up. It was nice having something to watch in the middle of night when Missy Moo was first born but now it's time to turn it off and get a life.
Die Foxtel. Die.
: )