Presumably only fare dodgers would think people who aren't entitled to free travel should get it!
On a more general point, I am very surprised that a hearing aid user can get a Disabled Railcard. I just don't understand it. I can absolutly see the rationale for a Disabled Railcard for someone who needs assistance to make the journey and therefore needs to have someone travel with them or someone who is unable to drive due to their impairment. Problem is you can't have a seperate eligibility test just for the railcard - you have to rely on some pre-existing criteria, e.g. receipt of DLA etc... Perhaps that's why hearing aid uses can get a railcard. When the Disabled Railcard was established then deaf people couldn't get Attendance Allowance or DLA (so they had to find some other criteria which would enable deaf people to get the railcard) but a legal judgement about 15 years ago meant that profoundly deaf people came within the scope of DLA care.
As a hearing aid user myself who is registered disabled on that basis, I don't think I ought to be entitled to a railcard, and would not complain if the eligibility criteria were tightened to exclude people like me (in which case I would get the inferior Network Railcard instead).
However, profoundly deaf acquaintances have given me examples of:
1) struggling to buy tickets from staff, due to the communication barrier; (TVMs don't usually sell certain tickets, such as split tickets);
2) being unable to access the (audio-only) train running information at certain minor stations without electronic departure boards, such as Patchway;
3) missing last-minute platform changes that were only announced verbally and not on the big screen, and boarding the wrong train as a consequence;
4) boarding a delayed train scheduled to stop at their intended destination station, only to miss the subsequent verbal on-train announcement that the train will no longer stop at that station, and ending up being over-carried as a result.
There is also a 'socioeconomic' justification in that deaf people do suffer discrimination and exclusion in other areas of life, tend to be more likely to be unemployed, or to be in low-wage jobs, and the Disabled Railcard makes rail travel more affordable. Of course, hearing people may also have a low income, and are not entitled to this railcard (albeit that jobseekers may be entitled to a New Deal railcard), so this argument is not particularly strong, in my view.
On a personal level, there have been journeys where I have had a choice between car and train, and chosen the train in preference to the car because of the 34% discount. However, this argument could equally be used to justify a national "34% off" railcard rather than one that is restricted to disabled people.