As a norm, it is completely up to the discretion of the cartographer that is making the map. Not to mention, its also often the same name that most people know it by.

More than discretion is the more common usage of that name in the English language. Older, european cities usually have a well established English name for centuries whereas western-hemisphere cities are newly translated. Therefore, most western hemisphere cities use their own name with only auxiliary words (like “new” and “city”) being translated to English. Now, because of the large-scale use of Spanish in the US, even cities with “new” tend to still use the original term “nuevo”. This is most likely due to the number of Spanish-named cities in the US.

On the other hand, English city names of Europe are as they have been established over the centuries. For example, Italians say Roma and Venezia, not Rome and Venice, but these names were established centuries ago and passed down as part of the language.

Typically there’s no official rhyme or reason for whether to call a city by its native name or its English equivalent. Some countries make concerted efforts to force cities’ native names into English lexicon, however; examples include Beijing (formerly Peking) and Mumbai (formerly Bombay). India has been particularly high-profile in this movement recently.

There’s also a country, Cote D’Ivoire, whose name translates to “Ivory Coast” in English but the country’s constitution and laws expressly state that their country’s name is not to be translated from the French for any reason. Other nations and organizations try to honor those types of requests, especially in diplomatic arenas.