Let's take Southampton - London Terminals season ticket as an example. Southampton is well outside the London commuter area so it's unlikely that people will use the ticket for commuting. However, this ticket comes with a large number of permitted routes covering as north as Basingstoke and Reading, and as south as Brighton and Hove. Therefore I believe the demographic of such season tickets is for businessmen who have a client base all over Hampshire and Surrey, and requiring frequent travel between clients.
If break of journey can't be done there is no point in offering long-distance season tickets which fall outside commuting areas.
I'm afraid you have a fundamental misapprehension of the factors that matter to people when deciding whether to buy a particular ticket. I daresay 99% of people wouldn't even think about the permitted routes of a season ticket and whether it would include routes other than those which are 'obvious'.
Pre-Covid there would no doubt have been a sizeable number of Southampton to London 5 day a week commuters, possibly even into the four figures. Even now there will still be some - although probably more who commute 2-4 days a week but for whom the season ticket remains the cheapest option.
The overwhelming majority of frequent business travellers have a car and use it for all their business travel - unless they are travelling to somewhere that is both well-served by rail, and poorly accessed by road (e.g. central London). The idea that a business traveller would hold a Southampton to London season ticket to visit clients around Hampshire and Surrey is frankly hilarious!
It's purely a question of utility. Is a system which allows loopholes, errors and mistakes to exist - and to be exploited as long as they are not exploited widely, fit for purpose? I've heard lots of defences of that arrangement, mostly along the lines that those who use such "good value fares" would lose out should the errors be fixed and/or the loopholes closed.
Again, I don't think anyone is claiming that the current system is truly fit for purpose. But there is no prospect of it being made fit for purpose, given the political bent of the government and most of the British population.
And although there are many flaws with the system, one of its few advantages is the fact that it discriminates based on willingness to pay. Which means that, in general, the maximum amount of revenue is extracted from each potential passenger.
It's an argument for the continuation of a privilege, but without any attempt to justify why that privilege should exist.
It's not though. It's remarking that the existence of good value and/or loophole fares is not concomitant with a lack of sensible validity for certain journeys. You seem to see them as two sides of the same coin - but they simply aren't.
I think it's also wrong to suggest that there is any privilege here. As has been said several times, anyone is able to find these fares with a little time and effort. In principle, I don't see that as any different to how with most utility bills, you can either leave them be and default onto a standard/out of contract price, or if you put a little bit of legwork into it you can compare the offers that are available across the market and go for something cheaper.
Furthermore, I don't think anyone is suggesting that there is an inherent right to continue to buy loophole fares. When they are found out, they are fixed. That's life.
In my view the routing guide and its associated rules should scrapped and replaced with a machine readable list of valid routes. It is an anachronism of a pre computer age. The "unpublished" restrictions should be the restrictions.
I think that would be acceptable and indeed a good move, provided the replacement included an industry tool that let you enter the details of the ticket you hold (or propose to buy), and then showed you a map of all the permitted routes (including mapped and shortest routes).
However some degree of human-readable text will always be needed for time restrictions, to convey the rules behind them. And this is where making unpublished restrictions the actual ones would be unacceptable; any restrictions that the TOCs want to enforce should have to be in the text.
But it's just a set of unique permitted routes and each permitted route is just an ordered list of stations. So the data structure is relatively simple.
It's not that simple at all when you dig into it. The Routeing Guide maps, for instance, are insufficiently detailed to enable the average person to work out what the validity really is - as not all stations immediately before/after a junction, or at the intersection of different routes, are Routeing Points, so there is a considerable degree of ambiguity. And some maps include stations that aren't Routeing Points (e.g. Harrogate) - even though it's undefined what contractual meaning this has. The use of Routeing Point Groups rather than individual stations also leads to a lot of uncertainty as to exactly what validity exists, or is intended to exist.
Determining the shortest routes based on industry mileage data is also problematic, as it includes links that have no passenger service at all (e.g. via Brigg), no permanently scheduled services (e.g. via Castle Donington), or no usable service (e.g. trains via Hixon towards Stoke do not stop at Rugeley). Which of these can you disregard when determining shortest routes? The Routeing Guide is again silent on this issue.
I could show you some data structures which are complex. The 100m plus routes between Falkirk and Ramsgate isn't complex. It' s a set of lists of stations, which is not as simple as it gets, but pretty close. But I will grant you that 100m plus is is quite a lot to scroll through if they were to be offered to you as a set, or carry around in your head as individual routes if you're an inspector checking tickets.
It's so long that it is patently infeasible for either anyone to have fully understood, let alone memorised, all routes. Whether it's complex or unusably voluminous is splitting hairs.
But I agree with the point about using fares which are any way out of the ordinary and the worry some people would have that they are going to be challenged. It's another good reason for there being a definitive list or process to check the routes on which any specific ticket is valid. But having such a list or check is not compatible with the need for the full validity of certain "good value fares" not to be made public.
There is no "need" for these fares not to be made public. Obviously most sensible people aren't going to voluntarily publicise them, but the industry is at liberty to (euphemistically speaking) "fix" them, as and when it finds them. But clearly it does not see them as a sufficiently important problem to warrant spending the significant amount of time and resources needed to proactively do so. It simply reactively "fixes" them.
There is: it’s called the National Rail Timetable and the National Routeing Guide.
Of course the NRG is highly ambiguous and even contradicts itself in some areas. So there is no clarity whatsoever over whether certain routes are permitted; the NRG is anything but definitive in that sense!
