Speaking of cultural norms, I came across a very intriguing, interesting one on my last trip to India. What I describe below appears to be the norm only in the Kolkata South Suburban section of Eastern Railway. I did not observe it anywhere else in Kolkata Suburban service.
My sister and I were traveling on a longish trip by suburban train in the Kolkata South Suburban section from Ballygunge to the end of the line almost on the Bay of Bengal at Namkhana (you can look it up in a map if you like - Ballygunge is the second stop from the terminal station at Sealdah South). Since we got on at Ballygunge which is not the originating station of the service, we piled in as is usual into an already SRO train, and were reconciled to standing all the way. Of course as the train proceeded further from Kolkata it started emptying out some and a few got seats, but mostly those that were standing continued to stand. Until we reached about the halfway point, at which the strangest thing happened. Everyone that was sitting stood up and offered their seats to people that were standing, and we managed to get seats! We were mystified and asked folks what happened. They said that this is a tradition on this line. People like to share their good fortune of getting a seat with their fellow passengers. I chalked that one up for collective sense of humanity of people who otherwise are poor to lower middle class in most cases on that line. Indeed south of a certain point on that line, if you travel at night you will find a distinct lack of electricity except on the railway, which is electrified, as are almost all busy line on the IR. Chalk one up for local tradition that is exemplary.
Naturally on the way back we knew what to do when the halfway point was reached, should the need arise. Fortunately we were by then in late evening traveling against the major outbound flow from Kolkata, so the train was not crowded enough to require anyone to stand.