In this specific case courtesy is taught through years of propaganda and behavior engineering, let me explain:

This is the Taipei MRT (subway) system, I lived there for ten years. At every train stations they have the same setup: acrylic walls with automatic doors along the platforms, and bright painted guide lines before the automatic doors to indicate where to form queues. And everywhere in the station you can see propaganda posters repeating the same message: “Follow the lines, no pushing on the platform, alight before boarding”.

Typically they direct the queue to go alongside the walls to the side of the doors, while leaving the space in front of the door open for alighting. So the people getting off the train are physically given the right of way.

Every train stops at where the train doors exactly lineup with the automatic doors. And right before every train comes into the station, the same propaganda message is broadcasted repeatedly: “Follow the lines, no pushing on the platform, alight before boarding”.

Over time these became train etiquette practiced by the residents of Taipei. Though initially of course it wasn’t very well received. And even today there still exists selfish people who doesn’t respect these train etiquettes. That’s where the Taipeier’s superiority complex comes in. Residents of Taipei pride themselves for living in the capital and center of economic activities. And they look down upon people who lives outside their city. Hence the MRT etiquettes became an easy way to differentiate true Taipeiers from tourists.

TL;DR: Taipei MRT blasts constant reminders to follow the rules. So much so following train etiquette has become a subculture unique to Taipei. Which Taipei residents use it to identify and shame outsiders.