Like manga, I hate it when they, for example, transliterate さん as -san, when there is an “equivalent” word for it, like Mr. but would it carry the same connotation as the source material? I cringe when I buy translated versions of Japanese literature due to this (which is why I stick to the source material), it just… does not sit well, I mean instead of writing -sensei, -senpai, or -sama there are “equivalents” in English for those but the catch is that would it work well upon translation?
Even English writings are sometimes translated into other languages maintaining certain terms in the original. Actually Mister, Miss etc. It’s a way to not lose sight of the original language - many times it’s not irrelevant that the action occurs in England, for instance.
It’s the same with Japanese: if you want to keep the reader always aware of it being a Japanese story, you use san instead of Mr.
It’s also common enough by now, that if you started using the English translations for -sama or Sensei, people would be confused.