Machine learning researchers aren't working on language modeling because they want to enable fake news.

They are working on it because it improves all downstream NLP tasks. See: http://ruder.io/nlp-imagenet/. BERT, Elmo and XLNet all fall under this use case.

For example if you're trying to recognize speech or translate some text, it helps a lot if you can start off producing something that is statistically grammatical even if the content is nonsense.