What (and this is a genuine question) gives the railway that culture where the private sector doesn't have it to anything like that extent?
I don't claim to have the answer to that. However I'd make a few suggestions:
1) Poor management leading to poor industrial relations
2) The railway being run without full resources being in place, leading to goodwill being required from staff on a regular basis, which makes it hard to manage performance issues when the next day a favour will be required
3) Staff ultimately having the upper hand because of the time and cost of recruitment/training, and the fact that the entry requirements are themselves stringent which reduces the supply of labour
4) Shiftwork, rosters and extreme shifts, which means staff have less time to see their families compared to other industries.
5) An industry that often moves the goalposts, so people sign up to something and then find the company wants to change things on a half-baked basis, often for no good reason other than new management making their mark.
In the end, if you take a job where you work every Sunday and that was what was on offer when you took it, why would you have issues with it? If you don't like the job, don't take it. Or if you see it as a way in, look out for other opportunities to move to with the preferred shift pattern as people leave.
What you'll find is that the newbies would be working near enough *every* Sunday, so unless you're going to contract them on that basis, perhaps with a clause that they can more to move mixed rest days as and when people leave, they'll be stuck with that, which I don't think is sustainable. As people leave this will ease the issue as eventually all the people on new contracts will become the majority, however how do you make this work on a roster basis? Change the roster every time someone retires and a person on the new contract takes their place? At some locations this process will take decades due to slow turnover. Rosters and shiftwork are difficult enough to plan round as it, without introducing all this complication.
The answer is simple, namely a 7-day roster with everyone on the same terms. However this takes us back round in a big circle to where we started, that seemingly no one wants to pay for that as it requires significantly more drivers.
I don't massively want to work weekends,
There we go, the fact that you and many others have the same mindset is why we have an issue.
which is why I haven't applied for a job where weekend working was mandatory. But if I did apply for such a job...
But presumably you didn't...