I don't know how much of it is culture exactly -- I find at Toronto's Bloor-Yonge station that people often do this -- they line up in two columns by the doors to let folks off before entering. I won't say it's done perfectly, but regular commuters seem to know it, here. It makes sense from a self-interest perspective: the faster you clear a path and allow folks off, the faster you can get on before the doors start closing. All bets are off at most other stations in Toronto though, they're often not busy enough for it to become an expected behaviour.