I have been in a position where I have learned a few languages for different reasons. I will go in order from most recent:
This is my family heritage, and the culture/traditions and people motivate me to continue. I am very much in love with all things Ukrainian. I continue to learn it to keep connected to my ancestry and to speak with Ukrainian relatives.
I briefly took this because I love Chinese films. I hoped that I could enjoy watching a movie more than just reading the subtitles throughout a film. Unfortunately my night school course was extremely short and didn't provide a lot of information. I retained nothing. For this reason it's not even on my list of languages because I don't remember anything of what little I learned.
I worked on the cruise ships when I was in my twenties. Before starting my first contract, I learned Spanish because I knew it would be useful for my work as many of our ports of call were going to be in warm, Caribbean countries. So I learned this for professional reasons, but did not use it any longer after leaving the industry.
I lived in a community at one time that had many German immigrants, and we had many German tourists each summer. I took a night school course for about a year, and then went to Europe where I made some friends in a few German-speaking countries. German for me was all about friendship and fun times, and to this day is a language I enjoy -- even though I never did achieve fluency.
I learned this language in school between grades 6-10. For these five years, it was not a choice but a requirement as a Canadian student. Because of this, I resented having to learn it. Unbeknownst to me, French is something I'm constantly exposed to, even though I cannot technically speak it. I find myself understanding it often as our labels are in English and French in Canada, so if forced to figure things out, I likely could. But having a conversation? No.