The 40 GBP re-issue fee will generate a lot of income for Ryanair. It is unrealistic that 100 per cent of all pax will show up at the airport with the printout. If only 10 pax per flight do not have their passes handy, each flight will generate an additional 400 GBP revenue. If Ryanair has 1.000 flights each day (pure guessing), we are looking at 400.000 GBP each day. For the whole year, this means approx. 150m GBP.
If you forget to take your boarding pass and pay extra then you will only do it once.
Idea that it would generate that much would have all the airlines doing it but reality is that it would be pretty small pretty quickly.