Printers in the home are slowly but surely dying (and good riddance to them!)
I think a lot of the fear of e-tickets comes from the amount of responsibility they transfer from the railway to the passenger. On CCTS and even PRT tickets, if the ticket office printer doesn't work, the TVM has a fault, or the magstripe on your ticket was faulty and won't open the gates, the passenger can be reasonably sure that it will not be considered their fault. However, if their printer doesn't work, their device's battery has run out, or the ticketing app doesn't work properly on their device, it is likely to be blamed on them. I can see why that transfer is very attractive to TOCs, but I think the concern caused among passengers is reasonable.
That said, I personally accept that the risk of those things happening is very small, and I have done many a journey on e-tickets now without any such issues arising. However, I'm not quite satisfied enough that I would be at all happy if the industry tried to push towards a locked-down format like the old m-tickets - I value the fact that at the moment, within reason, I can essentially store and display the ticket however I like.