> The way I see it, it is because a ZIP code can be associated with a list of cities that are categorized as “recommended city name”, “other city names recognized for addresses in this zip code” and “city names to avoid”. [1]

This one affects me personally and it bugs me programmers think that they know better than I do about my address when I try and enter the city name and zip code, then they "correct" the city name based on the zip code and make it read only.

a) what was the point of me entering the city if you were going to fill it in anyway ?

b) this has happened in the last two cities I've lived and is dirt common around a major metro area in the United States. Stop autocorrecting user entered data, let them be wrong!