For a more academic leaning explanation, I would suggest that what we have here is a
gift culture. I first heard about this concept in Eric Raymond's book on open source software, The Cathedral and the Bazaar, and Raymond's explanation is a lot easier to digest than the Wikipedia article. I highly recommend this page here as an edifying read:
The Hacker Milieu as Gift Culture
tl;dr --> "
Gift cultures are adaptations not to scarcity but to abundance. They arise in populations that do not have significant material-scarcity problems with survival goods. ... Abundance makes command relationships difficult to sustain and exchange relationships an almost pointless game. In gift cultures, social status is determined not by what you control but by what you give away."
I think this is actually pretty common in Internet subgroups, where sharing of intellectual property is its own reward. The fact that we've extended this to material goods is interesting though.