IME I needed both. I moved to an English-speaking country in my early teens, knowing virtually no English at all. Naturally I needed remedial classes, but IIRC

IME I needed both. I moved to an English-speaking country in my early teens, knowing virtually no English at all. Naturally I needed remedial classes, but IIRC I wasn't progressing very quickly, for I wasn't sufficiently motivated, and would have likely needed to take them throughout secondary school. That is until I got interested in computers. I devoured all magazines, books, etc. on computing I could get my hands on, and within that school year I "graduated" from the remedial classes. So I needed both to become fluent in English. I've got another example where I had motivation but not necessity. A few years later I became interested in manga / anime, back when translations of either were scarce. So I signed up for Japanese classes, and eventually even went to Japan as an exchange student for a summer. I continued to take lessons in college, until I'd essentially run out of classes to take. Having done all that, I would say my Japanese proficiency was merely functional. I probably could have passed JLPT N1 had I tried, but I didn't bother since I wasn't planning on working or studying in Japan. In this case, IMO I was reasonably motivated, but since the necessity component was missing, I never made it over the hump and became fluent. Finally, the kpop craze got me somewhat interested in learning Korean, but I barely know how to say hello / goodbye. I'll blame that on my brain plasticity though. :-P