Because, as a German academic once explained to me (years before the rise of LLMs), if you want your ideas to be influential you need people to read your papers, and you get a heck of a lot more readers when publishing in English than you do publishing in German.
Unfortunately, it's much more difficult to draw a clear line once you start allowing some AI writing tools.
Papers themselves become a source, something to check back on. They dont write themselves, it takes significant effort to make a high quality paper even with the help of AI.
And if you write a review paper that is a needed piece of literature, but this is also something that can be perfectly digested by a well crafted paper harness. and review hundreds of papers in the time you review 3.
what is it going to be? Speed of scientific progress or human crafted prose?