In the old days, if long distance trains were overcrowded it would be ordinary to see people sitting on their suitcases. Or even small folding chairs (shooting sticks) they had brought as luggage. I don't think that happens much anymore.
And it still happens today. fairly often.
I have (a few years ago now, it was during the last Ash Cloud incident)) travelled from Chester to Holyhead sitting on my flightcase in the lobby of the totally overloaded Arriva 3-car unit. ON that occasion, I had a reserved seat *somewhere* in the vehicle, but given it was standing all down the aisle there was zero chance of finding it. I actually shared said lobby with a 3-man Outside broadcast crew (with their equipment cases) and 2 other people, plus a number of passengers' luggage. We had to unload at each station to allow passengers on & off.
On a 90-minute plus journey that is not amusing. Thankfully, it was a Summer weekday, and the weather was gorgeous - as is the scenery if you can see it - so moods were good and conversations interesting.
Of course, the return journey was equally dire: the incoming service at Holyhead so late (over 50 minutes) as to vanish from the displays before even arriving (thumbs up to NRE online!) and connections back to Chesterfield missed - again, interesting people met & I did get home via Uttoxeter/Derby!
Sadly, Arriva's on-train & CS staff were singularly un-bothered, but did at least border on polite.
And I don't believe the situation on the N Wales has improved even now, at busy times of year. Best operator award? Not sure how Arriva achieved that a few years ago!
But back on topic, the "suitcase seat brigade" are alive & well.
I use my flightcase as a seat regularly, on stations, airports and trains, and on the East Coast peak trains there are often folks in the lobbies on their cases for an hour plus.
Looking overseas, I've had missed connections in S. Korea where transfer to a new train was allowed, but I had to stand halfway across the country as it was Friday rush-hour. Sat on the case again! You see it on the TGV & even Eurostar too at peak times, although strictly speaking it is not really supposed to happen...traincrew let folks on when there are delays & missed connections, in an effort to keep customers moving. Well done to the staff, and I don't complain for being enabled to get there at all when things go wrong.
As an aside, 2x TGV-duplex running in multiple is an impressive sight, and really very, very long. Seeing the whole thing at Marne-la-Vallee, Montparnasse or Lille is difficult: the station is too dingy to even see the end of the train. But at La Rochelle even 2x traditional single deck TGV is a great sight...over 500m of passenger train.
I'd agree that the difference between metros and longer distance trains is the typical journey time, as well as the price paid. I would object to standing for a long distance at the prices I pay over here. In Korea? Not really a problem. Peak Time 1st class from Seoul to Busan is only about £30 economy standby, less offpeak. An equivalent journey in the Uk might be London-Manchester, where we pay over £80 single at that sort of time. And you wonder why folks expect a seat!
(Note: I can't offer sympathy to those who want a row to themself at busy times. Man up guys! It is indeed nice if you can get it, but don't complain if you just get the one seat. Taht's all we pay for.)