Translation is expensive, it needs to not only to translate the story but the author's style and pun. A niche book won't be translated, especially in smaller languages (you have a bigger market when you translate in Spanish/French/German than when you translate in Luxemburgish or Nepalese). With that regard, english-language writer have the advantage of using a language that many can read, giving publishing company a glimpse of the translation potential.

With the power of "LLM" and translation app like deepl, it may work better in the future. However, at the moment, deepl is far from giving a professional grade results, especially when you have ambiguous word or a "specific but uncommon context". It work to share a blog-post/news article, but won't be sufficient to get fun to read book or an usable technical manual (However, corporate legal department may have a different opinion, it will be an interesting trial the day an accident occur due to an ambiguity in an automated translation)