The arts industry has been slower to adopt, but there's definitely penetration. Net artists have gallery representation, and lots of galleries and other art world institutions are selling online. The key, though, is that many of them are selling physical artifacts of digital art or experiences since digital art is hard to sell.
This is related to scarcity, but it's not the whole story. Part of the reason is that digital art is more recent in the history of art and doesn't have the same cultural clout among institutions and collectors as, say, an Old Masters painting. Another reason is that it's simply not easy to display digital art in a way that makes sense to today's collectors. Both of these things will change over time.
> There isn't really a big "internet famous" artist though, is there? Would Banksy count?
What exactly do you mean here? All artists today, whether or not they make digital art, are trying to attract large followings on the Internet. Many tailor their content specifically to look good on apps like Instagram. The boundary between who is and isn't an "Internet artist" is disappearing since artworks are beginning to conform to what we can experience online.