- Pretty much everyone is using the non-commercial license
- Because of things like Adsense, pretty much everything is commercial
Case in point: I love this set of CC sprites by Philipp Lensenn
They are brilliant, but to describe them as FREE as is misleading, because they're under a non-commercial license. Basically they're free, as long as you don't really want to do anything with them.
What's the solution? More people should use the commercial licence. But it wouldn't really be fair to, say, make a hit game and a bunch of money without any going to the artist. A better solution - contact the copyright holder and make a deal to share the money. But that scenario is no different than if the images had no CC license at all.
We need to come up with some kind of "revenue share" license, like the royalties radio-stations pay when they play songs on the radio. This way the artist would get a cut, but you wouldn't have to contact them BEFORE you use their work, only once the money rolls in. Would it work? Who knows, but at the moment artists like Philipp might be missing out on a chunk of change because game developers are afraid to use his sprites for fear of breaking the terms of the license.
Thankfully, most code libraries are MIT licensed, which is very permissive, so you don't run into this problem with code. And don't get me wrong - so far I haven't personally CC'd any of my own artwork, but maybe if there was the chance of getting some pocket money from it, I probably would.