I'm an ABC, and while my English is fluent, my Chinese is OK. If you ever need to talk to me in Chinese, assuming that's your first language, speak a tad slower than normal and try using basic/everyday words. If you crack a vocab-intensive joke or recite a famous phrase or saying, I'll probably give you a blank stare.
I'm learning Japanese solely to learn it. I think it's a beautiful language and heard a large chunk of people online are Japanese/in Japan (don't remember the exact words). I'm also borderline otaku (Okay, fine. I may still have a long way to go before reaching otaku status), so learning Japanese would be cool.
To be honest, I don't believe in learning a language because it's "useful" (unless it's for a career or something). If picking up another language is a personal choice, it should definitely revolve on which one you want to learn deep down in your heart. Otherwise, it's only a matter of time before one gives up or loses interest.
Alright, alright, alright, fine. I'll stop ranting.
Have a nice day!