People in all manner of professions are passionate about what they do, spend time and effort honing their skills, and want people to see and appreciate their work. Yet somehow, no one assumes 'Happy to work for free' unless it's in relation to writers.

By this argument, when we need a plumber, we just say, "We won't pay, but we'll show people what you did," and the best plumbers will queue up to work for us because they're passionate about what they do.