[skrebbel]

Culture. In fact, the GP answered it. Demos are all about awesome for the sake of awesomeness.

Sell it, and it wouldn't be "for the sake of awesomeness" anymore. And it'd be less fun.

There've been a small number of paid demoscene projects at some points, such as Linger in Shadows by Plastic (http://www.pouet.net/prod.php?which=50170), but even they were simply paid for the project by Sony, they didn't market and commercialize the demo themselves.

I guess it's simply that for most demosceners, once you not just doing it for fun anymore, it isn't really much fun anymore.