Kathy and Nedra ... great points!!!! But I am part of the choir here.
I think that WIP's also make you, the artist, really consider what you are doing and why. When we are posting a project at a certain stage, whether it is a mapping stage or shading stage or even I have run out of time to work today stage, we are also writing out in words where we are and what we have just done. So, at least for me, by working as a WIP I am paying much closer attention to both my work and the reason I just did what I just did.
For me it's a great way to figure out what techniques work for me and which don't ... so which techniques am I going to use in the next project. So being just a touch selfish and self-centered here WIPs aren't just for everyone else ... as a poster I get an awful lot of learning out of posting a Work In Porgress.
On another forum (WetCanvas) that uses WIP's I have done over the years a few WIPs that just went to "Whosits in a Hand Basket" and they were probably the ones that I learned the most. Not every WIP ends up with a Division Winning Work ... some end up headed directly towards the trash bin. Yet being able to talk out what happens, what might have been done different, what changes could have been made are where the real learning starts.
Susan