If we was talking about 20-30 years ago, hell, even as little as 10 years ago, when society was a lot more rigid, I would agree with you. People did expect to be able to get a meal served if they wanted.
(Un)Fortunately, times have changed, and with a more mobile and active society plus the reduced journey times, people when planning long trips, such as travelling on the full length of the Highland Chieftain, now plan around it, and take supplies with them. I did exactly the same thing in May when travelling to/from Perth with my sister and brother in law. We knew we had an hour in Edinburgh between trains heading north, so we planned around that. Coming back South, we was on the Highland Chieftain between Perth and York, and were able to get hot sandwiches on board, plus the trolley went past us 7 times between those stations, so we was able to get drinks when we wanted.
With us also having a 30 minute change at York, we was able to plan around that. While I don't claim I speak for everyone, I do see quite a few people on long distance journeys who do bring supplies, and only "top them off" from trolleys and buffets.