I'm going to answer with a more personal story. I did my doctorate at Laval University, and I took some English courses as part of my studies. Given the completely francophone environment, it was very hard for me to apply what I had learned in class. That's a scenario that I'm putting out, and it may be false, but based on my experience, Canadian students prefer to learn Spanish or Chinese because that enables them to speak to foreign students. They want to discover other cultural horizons.
It's been clearly shown that language is one of the vectors of culture. They figure that, since English is one of Canada's official languages, they will have to learn it in one way or another. It's part of their identity; it's not something new. I think the desire to learn new things, to discover a new culture, encourages students to turn to other languages.