Languages don’t have to do it. Languages are organic and evolve constantly. A language is not a set of rules, it’s what people speak. The books just try to formalize it. But each language has limited set of sounds, so older names of places often used only those sounds because people literally couldn’t pronounce other sounds. Or when the name is something totally different, it’s usually very old names for things, ans they often get changed! (recent examples are Turkiye and Kiwiv). You also can’t force people to use certain words, it either comes naturally or falls out of use.