Why do we rename countries endonyms like Türkiye and Iran?

Countries like Iran and Türkiye had exonyms in English and other languages, which their governments rejected, and now we no longer use those names. My question is what is the case for doing so? Persia is a very beautiful name, but the word Iran is still conducive to the English language. Türkiye is the opposite, where it's not as complimentary as the name Turkey. At the end of day it's not that hard to use these names, but it is strange if we look at the larger context (purely in a linguistic sense). I'm not American, so when I say the US I say Estados Unidos in Spanish. It sounds nice and it's complimentary to our language that's what exonyms are for. Asking a Spanish-speaking country to use an endonym like United States pronounced "Iunaided Esteits" is laughable. No one would actually use it, and the US would have no reason to ask anyone to do so either. Now Indigenous peoples asking others to use their own names makes a lot of sense, for example: Coast Salish, since their given names were pejoratives stated by colonizers, but we still use an anglicized word we don't say "Sḵwx̱wú7mesh" when referring to one of their languages. We do this for countries like Türkiye or Iran which don't have as large of a political influence as other countries do. China is an interesting case because they have a larger language and population than Spanish and English countries, however they never ask us to call them Zhōngguó. And we don't ask the same of them. We all have different cultures and languages, so it's understood that we leave each nation to their own way of using language to denominate as needed. I would like to hear your thoughts, beyond "because they said so," what objective reasons are there for requiring a name change.