Why learning English?

I’m currently learning Japanese and Korean, and because I’ve been using YouTube for comprehensive input, I’ve started seeing a lot of ads about Taiwanese English learning. It got me thinking—if we’re forced to study English from junior high and high school, and now even in elementary school, with some continuing into college, why do we still need to learn it? What’s the point, and how can we keep improving after already studying English for more than six years on average?