That's your opinion. That doesn't make it the rule. Dribbble "shots" are intended to be smaller snapshots of a project. That plays much better with WIP type shots then polished, finished pieces. While a lot of the work on Dribbble doesn't feel like "WIP" work, the majority of it is—that's just because it's full of talented designers. You'll see several iterations of the same thing (ie WIP). Plus, I'm fairly certain that was the intention of Dribbble, regardless of what you think.