Not heard anything internally as I work for one of the TOC's mentioned, but I will say that there are plenty of complaints when people are able to purchase tickets when the train is already full.....many people already think a seat comes automatically with any ticket. One of the TOC's booking systems blanks out services when they're fully reserved now with the reduced amount of reservations allowed.....
This is indeed the main reason for compulsory reservations being introduced.
To put a bit more flavour on it, there have been many (pre-Covid) instances where trains leaving Kings Cross especially (and also other stations) have been grossly overbooked, with many customers having to stand for very long journeys (such as London to Edinburgh). I've seen this myself several times on Fridays and Sundays.
It goes without saying that this leads to a very poor customer experience, and a view (both by those directly affected, and those who were on the train but had a seat) that train travel is not good at all, at any price really.
But we need to ask: why did this happen? The answer was that it was because, although all reservable accommodation was fully reserved, online booking engines continued to sell tickets, even though there was no seat for the ticket holder to sit in. You might think that this is the fault of online booking engines then, but that isn't actually the case - with the old National Reservation System (NRS) it was not possible to tell whether there was no availability because the train was fully sold out, or because reservations were not set up for some reason - the response was the same.
Since the pandemic started, a new reservation system (RARS2 - Rail Availability and Reservation Service) has replaced the previous one. This is more sophisticated in a few ways, and it should be possible (so far as I know) with this to be able to distinguish between trains that are "sold out", and trains that don't have reservations set up (although they ordinarily would).
As a result, it should also be possible for online booking engines (and also station TIS and TVMs) to indicate that a service is fully booked and that, although you can buy a ticket for it, you are not guaranteed to get a seat, and that you should consider getting a different service instead; this is quite a manageable UX challenge really.
So that's it, really. There isn't actually any need for the very blunt approach of compulsory reservations for all inter-city services in order to solve the problem that I mentioned at the start. (There was a year ago, when we were on the old reservation system, but that problem has gone away now.) It's a problem that can be resolved through understanding and using the available data, to nudge customers' behaviour in the right way. And it isn't even that difficult to solve, really.
Most importantly of all, the context that we find ourselves within at the moment must be appreciated. The railway desperately needs to attract back previous customers
and to win new customers (the latter to fill the revenue hole left by a drop in commuters and, probably, business travel). And to do that it has to avoid unnecessarily creating situations where customers have every right to be aggrieved, and are likely not only to not travel again, but also to tell others about their experience (both through social media and through their own social networks). If the railway doesn't solve problems like this, then revenue won't get to the levels we need it to get to, and even more cutbacks and closures will happen.
