In one of my classes at university in my first year, I had a classmate who promoted World Campus. She explained what it was and invited us to a presentation. That year I did not go, but the next year a different classmate introduced me to World Campus again and that year I signed up. I decided to do so because I was very much interested in Japanese culture, but my knowledge was limited to Japanese pop-culture and history. World Campus offered me a chance to get to know things about Japanese culture that I either did not know or only had theoretical/academic knowledge about through personal experience instead of through textbooks. It offered me the chance to get to know Japan a regular tourist doesn't.
Another reason why I decided to join was that I wanted to get out of my comfort zone and push myself. I hesitated about joining that first year because despite my interest in the country, I was too nervous about having to perform once a week and interact with the host families. But I wanted to grow, and just went for it.