Because AP language courses are ones where you finally actually get to do substantial reading of literary texts as they were meant to be read? Because speaking a language well can get you opportunities you might not otherwise? I got a summer grant for senior thesis research studying low cost housing in London and Berlin. If I hadn’t taken AP French in high school I don’t think I’d have had time to learn two languages in college. I did archival research and talked to residents as well as photographing buildings.
Not every non STEM kid has to take a AP language courses. My kid who liked history took 3 history APs, but didn’t continue with Latin beyond Latin 4 junior year. He ended up studying Arabic in college. His major required four years of language study in a modern language or fluency. (If he’d known that he’d have taken a modern language BTW.)