Ah, but I think this arrives at the crux of the issue. There's this 'thought', for want of a better phrase, that by buying a ticket before boarding you have somehow committed an altruistic act.. "oh, I have a ticket, please check it, aren't I a law-abiding citizen" and then the dichotomy of "i've bought a ticket I want it stamped to "prove" I've spent money travelling"...
I'm not quite sure where I'm going with this but it's something along the lines of (pun, intended), that people ultimately think the railways should be free and any cost suggestion they're paying less than the 'other man' is somehow unequal.