Hey, if we didn't play with dirt, we wouldn't have figured out that you could make walls and build houses with it. If we didn't play with rocks and chisels we wouldn't have figured out that you could make wheels (ok, the second one is pushing it, but whatever).
Point being, a lot of innovation comes from people who begin with just playing around with something. That innovation can either directly or indirectly impact every other OS, sometimes in a big way. That is why it's good to have other projects (sometimes smaller, sometimes bigger) that people can play around with in their spare time. And if you pay attention to them, you might have some ideas for your own project, possibly better than the original idea. Of course, if you don't code and don't share your idea, it's worthless, so the other project would similarly seem worthless to you.