@cstross I remember having a discussion about British Rail vs Privatization, I wasn't exactly pro-Privatization but I argued it was more complex than "Utopian government-run system vs Greed" which, you know, is too nuanced so people took at as meaning I was pro-privatization.
Anyway, the person I was arguing with came up with a long list of ways in which British Rail was "better" (faster, more on time, cheaper, the usual things people are sure happened) including, amazingly, that the trains were "cleaner".
I pointed out exactly what you're pointing out - he was looking at BR with rose tinted glasses. The reality was every train before the early 1990s was basically caked with cigarette ash - and that was in the no-smoking sections. My first memory as a kid was riding the train from Aylesbury to London, with ash on the floor, on the doors, on that weird metal dotted thing attached to the doors that smokers were supposed to use to stub out their cigarettes, and that yellow haze on everything.
It wasn't that BR was bad because of that of course, had BR survived to the 2000s then, yes, quite possibly the trains might have been cleaner than those today. it was that BR lived in a naturally dirty era. So somehow remembering the trains as "clean" means you don't really remember the trains back then.
(On a related note, was rewatching ET recently and thought "Wow, they got it close", the communal areas of the home in that film had that dirty haze around them even if I don't think anyone are actually shown smoking, the kids bedrooms were a realistic mess.)