No, you’ve missed the key point that TOCs would need total freedom to set price and volume. Under current contracts the only way to maximise profit is to maximise revenue. TOC private management understands discounted tickets have a role to play here (ask Lumo or Ryanair). DfT is hands-on at the moment and doesn’t get it at all - useless.
I've not missed the point at all.
You cannot compare rail fares to the likes of Ryanair. They, and even Lumo, can choose to discontinue services at the drop of a hat if they aren't profitable. A rail franchise (run on behalf of the Government) cannot (and must not) be able to do that.
My fear is that at some point you end up with a train operating company that's a bit strapped for cash (happens pretty frequently, especially if they're coming towards the end of their contract). They then decide to cut the number of cheap advance tickets, none of it is at all transparent of course.
Let's look at London to Manchester. A passenger need never pay more than £98.10 return to travel at the weekend. The train companies would love to increase that but thanks to regulation they cannot. If they were able to increase the price we'd have all sorts of PR bluster about cheaper fares, and they would be some, but at inconvenient times like 05:30, 22:00 etc. The popular departures like 10:00 would become unaffordable.
Then there's the lack of flexibility with Advance tickets.