Could it not just simply be that Ryanair narrow down the list of acceptable ID's so that their staff can comfortably and confidently recognise and validate authentic ID's from forgeries?
If you allow all sorts of quasi official ID's whether military ID, company ID, student ID, old out of date driving licences, bank books, pension books etc then you open the door to all sorts of abuse. Can we really expect checkin or gate staff to be able to positvely identify these little used ID's as valid? Its all downside if they get it wrong and no significant upside if they allow their use as I can't see there being much of a "no passport, no drivers licence, no Government ID" market niche. Better to have a couple of hundred sad stories each year than one terrorist getting onboard a flight using some obscure form of ID.
If this old lady is fiercely independent and actually booked the flight herself on the internet or over the phone and made her own way to the airport then I both admire her and feel sorry for her because she didn't read the terms and conditions. If on the other hand someone in her family made the arrangements and either didn't bother to check out the terms and conditions or thought the checkin staff would turn a blind eye to the passanger identity rules in this day and age because she is an old lady then I'd lay all the blame at the feet of the person who arranged the trip for her, they didn't take good care of her and shame on them not Ryanair.