You have then, as in California the BART ticket gates used to print on tickets as they passed through, although they no longer have any paper tickets. They were quite elaborate, they printed a running total of the balance left on the ticket. A paper-based version of Oyster PAYG!
Well it's not a nationwide or widespread thing there; I didn't take the BART but travelled on local operators in various cities and didn't experience this.
It sounds it is actually an antiquated niche situation, not at all how the original post portrayed it, so my point still stands!
I had to very carefully explain to our expnses team why an open return ticket London to Newcastle was better value than three separate singles London-Newcastle - Leeds - London: the concepts of "any permitted route" and "break of journey" both being alien to them.
And incidentally a I have yet to find a journey planner (NR, Trainline, whatever) that recognises that you might want to use different via points in each direction - if you specify "London to Newcastle return" you can only add Leeds as a via point in both directions, not one direction only.
As
@plugwash says, one provider does this:
IIRC trainsplit/trainscanbecheaper allows specifying different via points for the two directions.
and to do this, on the new.trainsplit.com site, go to advanced options then deselect "use these options for return":
By the way there isn't any point using Trainscanbecheaper; it's the same as the old Trainsplit.com but with splits turned off. The new Trainsplit site simply allows splits to be turned on and off.
I once got challenged as to why I'd bought a peak instead of off-peak ticket. Erm.. because the meeting started at 9:30am and I did not want to be prosecuted for fare evasion?
Off Peak varies by route, e.g. York to Macclesfield is valid from 0715, but if you go to Stoke you can't depart until 0900.
You should not be prosecuted for using a time restricted ticket at a peak time unless there was evidence you did so deliberately to avoid paying the correct fare; the standard course of action would be to charge an excess fare.
I'd rather see single-fare pricing than any more complexity being added.
Some TOCs had such fares prior to "simplification" (circa 2007/8) however they abolished them to fit in the new structure.
TOCs no longer feel bounded by "simplification" so do all sorts of stuff against the principles of it now; I guess that could justify a new "re-simplification" which would be an excuse to put fares up. But let's not go there...
!