Learning foreign languages can spur you to read more books, and books you might not have read before, thereby making you more informed.

Recently I learned Arabic to directly work with some sources in my branch of academia, and to be a better guest who can make some basic conversation when I travel to über-hospitable Arab countries. But going through the reading selections in my Classical Arabic textbooks revealed a whole canon of interesting literature on Middle East and world history over centuries. I have been eating that stuff up, and I probably never would have learned about it through languages I already knew; indeed a striking amount has never been translated.