We have many railcards and most stations have racks with all of the individual ones, but I rarely see anyone take any. Maybe now we have the digital cards, it's time to streamline and produce a simple leaflet covering all cards - and for websites to have a wizard style system to establish what railcards might suit someone (what's your age, how much do you travel, do you have children, do you travel with a partner, are you a full time student etc).
I expect a lot of people know the obvious railcards, like young persons (yet don't know it can be for older students) and senior or disabled, but do they know the others? Just as I bet many people have no clue about plusBus.