It does strike me that many members of the public who know far less about rail than people on this forum are just getting on successfully with electronic and mobile tickets without the concerns and hypothetical issues raised here being a problem.
It's like with lifts and stairs: for most people, if the lift is out of order, you can take the stairs. It might be less convenient, but you can do it if necessary.
For a small number of disabled people, if the lift is out of order and the only other way off the platform is stairs, they cannot get off at all. So the lift option is important even if very few people need it.
There are also a small number of people who, for various reasons, cannot use mobile devices, or sometimes the internet, at all. Not in the sense of they'd have to learn something new, they are physically/mentally unable to do so.
I would hope that, despite the headlines every time a passenger with a wheelchair gets left on a train or similar, people on a rail forum - many of whom are rail staff - are more disability aware than the average person, especially with regard to how disabilities can affect your mobility.
To dismiss these issues as "hypothetical" sounds to me like you are not an expert on this issue.