As a big fan of Shell, I agree with x-shaney-x, and it's something I noticed early on. It's nothing to do with Unity or desktop icons - the overview is like Android's home screen or Win 8's Start screen, and it ought to be the default fallback place to be. Partly because it is, but inconsistently.
At first, I did find t odd that when the last window on a workspace is closed, I drop back to the Overview. I got it, though, when I realised that the Overview just is the place you "fall back" to. So then it became odd that this doesn't apply to the moment I log in - naturally, the first thing I'm going to do is launch something - and why I can select an empty workspace at all.
I don't buy the argument about a clean desktop. I want my desktop clean so crap isn't hidden under my windows, or competing for my attention with non-maxed windows, not so that I can stare at my pretty wallpaper. I also want to access my stuff as efficiently as possible. So the default position when nothing is running ought to be the place I keep my stuff. (This is not the same thing as the overlappity mish-mash of the Win XP-Gnome 2 way of doing things, so please don't think I'm getting nostalgic, though I suppose it's no different from combining the benefits of desktop icons with the interaction mode of the Start menu, which is exactly what Win 8 does, although Shell also tosses in window management.)
But truth be told, I'd settle for a fix to the first problem, that key bindings don't work in the Overview.