I think it's just that in the past, you would need X free time, Y motivation level, and Z skill level (partly tradeable for X and Y) to create something like this, and now all of those values are smaller. So it's 'economics' in the straightforward sense, because not everyone could afford to spend X hours on something they weren't going to monetize, and also in the sense of the incentives shaping people's productive/creative activity.

(As for whether it's a good thing, I'm conflicted. It's cool to see more stuff like this, but if it crowds out the more intense passion projects, we lose something too.)