If you learn Mandarin, you’re learning how to talk to more than 1 billion more people. Spanish, about 500 million. Arabic, about 300 million.
Learning a foreign language opens some gargantuan doors in terms of speaking to other people.
We are, like it or not, increasingly becoming a global society. To function, we need people to be able to speak with those who are outside of our borders and outside of our primary language.
I absolutely am in favor of language instruction beginning at younger ages. I was given the privilege to take Spanish in 8th grade (My middle school was the only one in the area to do that, and there were a select few students who were allowed to take it). I think by the start of middle school, a foreign language should be one of the major classes, right alongside maths and sciences.