Isn't volunteering a job?
I don't see why would working without pay for a non-profit organization not be considered a legitimate occupation?
Would you rather get paid for work you don't care about doing or not get paid for work you're passionate about? And don't tell me that everyone can get paid for what they love doing! Most people would quit their paid job if they suddenly won a jackpot. And I think people many people are jealous and annoyed of those who can afford to do what they love without pay.