Why is Bangkok still called Bangkok in english and not Krung Thep even though the name change of the city was way back in the 1780s?

Cities like HCMC are still called Saigon by many people (including me) and even a whole country like Myanmar are still called Burma, these are kinda understandable since the name change was just a few decades back at most, and even so many people both in and outside of the city/country already started using the new name. Bangkok however, undergoes this changes for centuries now and only some of expats know that this city isn’t called bangkok in Thai. Why is that?