If you ever teach a group of kids you quickly learn that interests, personality types, needs come in a wide spectrum. Whats in the "core curriculum" and its effects are not predictable. For example, I had French classes for 4 years and can't speak, read or write it to save my life. The teacher wasn't bad and kept telling me, who knows maybe one day I'd move to France. As a kid, I thought the whole thing was ridiculou…
When I took ASL I remember them saying the reason ASL was accepted as a foreign language was because it has a culture that was taught along with it. It may or may not be taken seriously when taught, but a lot of people grow up in a bubble and don't get exposed to other cultures.
I've lived with a bunch of people that were fluent in English, but it wasn't their first language and others who were English native but studied foreign languages more seriously. Learning another language makes you think more about your own language. One friend said her teacher gave her a basics of English book early on when studying Japanese.