Films can work in a lot of ways.
One of the rarest, yet most effective, is that a film can show you worlds you don't know, can make you understand the complexities, joys, and problems of people who are not like yourself. When done well, this kind of film can have the sort of intense impact only possible in a revelation. I have no interest in bicycle racing, nor bicycles in general. Hell, I never even learned to ride a bike. But American Flyers showed me the world of bicycle racers and made me care about it, and perhaps even understand a little of it.