Nothing ........ but where it's going to cost money is when they stop charging £40 to print a boarding pass, or £160 if it's a family of four, or when they stop charging £50 to check in a bag that's a millimetre too big, or whatever it is for a bag that's 500 grams overweight, or when they stop trying to sell scratchcards on the flights. Then the staff start to lose their bonuses for 'extra ancillary income' and they are going to be miserable and those smiles won't be there
I don't see why people "forget" or "can't" print out boarding passes, its not rocket science and not the hardest thing to do. There is no excuses for not having them and its made crystal clear when booking that it needs to be done. If the majority of passengers can follow rules why can't everybody. You don't leave your house without a passport (some fools do) but its fine for some passengers to leave without there boarding card.
If you book rail tickets, you don't turn up to stations without tickets printed or your reservation number. You learn how to read in life so the minority of passengers who fail to follow T&C's should pay a heavy price for mistakes.
If FR reduce charges or relax charges for peoples mistakes, everybody will be paying through higher fares. FR will make back all the money they could lose by becoming more customer friendly. I believe the boarding card fees should stay and even be increased more as once they become high enough people won't forget things.