Will that result in a charge or other problem?
(On the London Underground, it would result in a charge, as the system is designed to assume you exited somewhere but somehow managed to leave without tapping out.)
On day one there was no noticeable symptom. But if your Oyster only had a season ticket for outer Zones and your route was via Zone 1 the system had surcharged you, and when you tried to travel the next day the Oyster has negative balance, you can't use it until you pay off the excess. This infuriated some travellers, when in reality they had actually been cheating (presumably in most cases without realising) previously.
Today Oyster can actually track if you insist on taking the long route, you tap pink validators at key interchanges you'd need to pass through to do your slower and less central route avoiding Zone 1, and the system will go OK, fair enough, you really did go the long way so keep your money. I expect very few people do this.
I doubt this. Even as a child I knew that a travelcard must be valid for all the zones you travel through. Of course, if challenged, someone knowingly cheating would claim they didn't realise.
> you tap pink validators at key interchanges > you'd need to pass through to do your slower > and less central route avoiding Zone 1"
Wow! I had no idea this was a thing. I moved away from London in 2010, and now I'm curious to know whether this was implemented before or after I left.
I used this frequently at some point, but it is now so long ago I can't remember where. Especially with many London Overground routes, it's not necessarily slower.
Even worse: they're asking NON-riders to see an agent twice
Presumably on the second entry you will be riding the train.
https://tfl.gov.uk/fares/how-to-pay-and-where-to-buy-tickets...
[Edited to add: Stupid web site doesn't have working fragment markers, click "Same Station Exits" near the top... ]
In practice, as it explains elsewhere on the site, these charges are mostly to discourage attempted fare evasion, and if you're a regular user who just does this once in a while it'll delete the journeys after it decides this isn't suspicious after all, otherwise you need to talk to a human if you really didn't travel anywhere.
I wonder: if there were better enforcement of fares in San Francisco, would public transport be better? Right now, I almost never use public transport in SF because ~100% of my journeys would take 2x to 3x as long as they do by car. This is very sad for me, having previously lived in two cities with excellent public transport (London and Beijing).
Are they not present sometimes? Yes. Are they slow / overrun by people? Sometimes. But that has little to do with the fare.