Where is all the open source Art?

Code - side:

The world pretty much runs on open source software, - Linux, Apache, MySQL, Memcached, ... the list is endless. Almost every company with any meaningful tech is using some open source software. Some of the best software developers invest countless hours of their time into open source movement; it's a point of pride for them.

Art - side:

The open sourced art is pathetic! It's a tiny selection and of poor quality. Whenever you see open sourced art, such as on Behance.net, there is almost invariably a demand to put the name of the artist in the credits. If your average website had to put in the credits the names of all the contributors to all of the softwares it's using, that list would thousands names long.

Question:

WTF is going on? Do software developers in general have generous hearts, while artists have poor hearts? Do software developers live in a world of abundance where sharing is the norm, while artists live in a world of scarcity where hoarding is the norm? Do software developers earn so much for their work that they can afford to share, while artists are paid so little that they need to squeeze every last penny out of their art? Is there some systemic issue at work here? I would like to understand what's going on here.