Okay, I'm going to bite.
First of all, as others have mentioned THE UNIPNS WANT SUNDAYS INSIDE THE WORKING WEEK TOCS DON'T!!!!!!!
When I first joined the railway, c.20 years ago, I worked for LT and Sundays were inside the working week. IIRC the working pattern was two weeks earlies followed by two weeks lates with rest days on a 4-week cycle, thus:
Week 1: Sun, Mon
Week 2: Tue, Wed
Week 3: Sun, Thu
Week 4: Fri, Sat
The result was alternate Sundays off and one long weekend off every four weeks. From what I recall this worked well.
When i joined the mail line railway, I was somewhat surprised to find that Sundays were outside the working week and paid as overtime. I have been on committed Sundays since day one and the set up at my TOC is that if you need a committed Sunday off and alternate cover can't be arranged you either work it or have 5 days marked against you on the equalization count (this reduces your opportunity to work additional Sundays)*. Over the past 10 years, I have yet to have 5 marked against me as thankfully, when I've had to make myself unavailable for a committed Sunday, cover has been available.
Overall, the committed Sundays system seems to work well at my TOC and cancellations due to traincrew are invariably lower on Sundays than Saturdays.
With regard to other industries treating Sundays s a normal day, I would like someone to provide me with a list of those where this is genuinely the case. Last time I checked, retail operated reduced hours on Sundays, the GPO was closed and the NHS provided "essential" cover only outside of Monday-Friday daytime hours. My neighbor's partner had to spend most of last weekend in pain, albeit in hospital, because his condition won't immediately kill him and the surgeon isn't required to work weekends.
As for traincrew being paid to sit at home, as others have said, this mostly happened at the height of the pandemic when services were substantially reduced and depots were subject to social distancing requirements. To the limited extent that this still happens at my depot, it is subject to:
1) The number of spare turns greatly exceeding the number of open turns
2) Stay at home spares being required to book on by phone at their booked time and being ready to drop everything and get to work at a moments notice. In other words it is effectively being on-call. The upside to the company is that messrooms aren't full of spares, The upside for the employee is a reduced fuel bill. In other words win-win
Rant over (for now)
* This applies regardless of the reason for needing the time off, other than Covid, though you can appeal to your line manager if you are genuinely sick