Earlier quoted context omitted.
You raise a good point here. There's a degree of trust here, too. Trust placed on the consumer to do the right thing and pay. I'd also say there's an additional consideration being put forward by the operator: sometimes people just need a ride every now and then. I've been Japan three times now and I've seen several incidents of the guards letting people just walk through without a ticket because they explained some…
I've went through gates without ticket several times for reasons like access to coin lockers or switching to the other track when I've entered the wrong one. Gate guards usually hand you a slip that explains the situation at the other gate or when leaving again.
The sign said the machine to issue the seat supplements was at the east entrance — the other side of the gates from me, of course.
The guard at the gates understood me, but said I must exit back the way I came, i.e. all the way back to the west entrance. That side of the station 'belonged' to the other railway company, and there wasn't a machine to sell the ticket I needed. I could either walk the really long way around by road (not through the station) or queue at the general ticket office.
So I missed that train.
In general, I found the train ticketing system for regional or long-distance trains needlessly complicated compared to Europe, with base tickets, express supplements and seat reservations all separate fees, and coming as 1, 2 or 3 bits of paper depending on I know not what.
On one occasion a journey with a transfer came on 7 separate tickets. (Of course, the Japanese approach to this problem is not to simplify the ticketing system, but to invent a machine that can suck in all 7 tickets, cancel the relevant ones, and discharge them neatly arranged.)