The difference would be that, where there is a period of regular disruption due to external factors, such as suicides or snow, the affected TOCs would not be operating a 'free' service. Which is what sparked this thread.
Why is this a concern?
Your argument seems to stem from the idea that as long as you have taken *something* from the service offered then it’s wrong to receive a full refund by way of compensation.
Hence my pizza analogy upthread which you unsatisfactorily countered by suggesting “well you’d be buying a *high quality* pizza” and that this doesn’t apply to railway journeys. But it does. You can’t have the scenario where someone from the TOC stands up and says “look, sometimes it’s really crap, okay, so we’re still going to keep 25% of the fare. We never said it’d be any GOOD.”. That would be Monty Python-esque.
The reason that you would receive a full refund on a bad pizza you’d had a few mouthfuls of is because that’s a neat resolution and good customer service. That’s it. And that’s why you get a full refund when you have a bad journey.