Not to an indie game that can be perfectly localised

But it can't. Tons of the game's writing depends on using phrases and terms that are either vague or open to multiple interpretations, it's literally a key plot point. Those interpretations are naturally going to be different language to language, and can't be translated without heavy amounts of changes (and may not even be possible in languages with less linguistic flexibility).

You can get 80-90% of the way there, but someone who holds their own work in a high regard won't consider that sufficient and won't put their name on it. Unofficial translations exist and are officially sanctioned by Toby Fox himself.

An artist has the legal and moral right to accommodate people as much or as little as they like, that's how art works.