It's hard to make money for creative endeavors, for several reasons, and there are generally two ways to make money from them: put everything into it and hope for the best, or have a "real job" and do the creative thing on the side. Regardless, and personally-speaking, I prefer doing creative things for free because that's the best way to keep my interest-level high.
I'm glad I don't work for you.
edit: More to the point, I think this idea that people don't work for money is one pushed by management at the expense of the workers, and when I hear employers putting that out there, I assume those employers are... bad to work for, because they think that by being manipulative, they can get you to work for less.
Usually, those employers have less pleasant cultures and pay less than employers who simply pay more than their competition.
I don’t employ anyone, so you don’t need to worry about whether I would hire you to keep doing your hobby and kill your love for it.
Myself, and a few other developers, refuse to monetise our third-party apps for the video game Destiny because doing it for free means we have no obligation to any customers. If I was being paid to do this, I would enjoy it a lot less.
In some cases, it could be less output, or lower quality. Money (or other explicit rewards) changes the psychology of doing work vs. volunteering it. It adds pressure, makes the work feel like a job instead of a hobby, and can lead the person doing the work to choke on deadlines, slack off, look for shortcuts, or even give up entirely.
Of course, people providing valuable services to a for-profit business should be fairly compensated, and companies shouldn’t be trying to exploit volunteers.
But monetary “incentives” are in general quite a terrible system for eliciting good work.