(2) Do you print them off for your parents? Or do they print them themselves? Or are they confident enough to book and use their own on their phones? Genuinely interested, assuming your parents aren't about 50 or younger!
My parents are in their 70s. They show them on their phone, and book them themselves. On occasion where I have had to book tickets (like Eurostar), I have just emailed them the tickets or sent the Wallet passes on WhatsApp.
Also I'm chuckling at the idea that "about 50" seems to be the cut off for an elderly person. My parents aren't what I'd call elderly, which has connotations of slowness and infirmity, they're just old. Most people in their 70s now can use computers, smart phones, etickets, and so on. Eticketing is the only medium available for a lot of things now.
(3) And a bank account to buy their own tickets?
This point was addressing the transferability of etickets which you said wasn't possible. Young teenagers don't have their own money; they don't buy their own tickets. In any case, yes, most 11-17 year olds have their own bank account; banks have products, with debit cards, specifically for these young people. I am 37, and had a bank card when I was 12 or 13. This was common even in the late 1990s.
There are also prepaid cards now which hold a child's allowance. Kids are using bank cards like everyone else.
(5) I'll concede that a lot of passengers use them, but we don't know whether they prefer them, or just think it's the only option these days. I'm sure younger folk who probably used computers from school age and wouldn't know any different are absolutely fine with them, it's second nature, but not everyone (especially older people) works with a computer day to day, or is confident enough to rely on technology for something with the potential pitfalls of showing a rail ticket to a RPI.
Yes, it's not for everyone, but hearing the consistent misconceptions about what they are and what you can do with them is frustrating.
They are the most popular ticket medium for a reason; most passengers overwhelmingly prefer them. The railway was late in introducing them, and passengers consistently asked for them, especially after the advent of apps like Wallet. That etickets also have benefits for train companies only hastened their rollout once the technology was adopted.