Left sidebar zone A functions and widgets- why not in other zones?

Why are there widgets in the left sidebar user admin that are not usable/draggable to other zones? For instance, the user messaging widget, which I want on the user profile page.

If I can get the A zone sidebar functionality onto other pages, I can use CSS to get rid of the left column all together... which would make my network fit neatly inside an iframe that can take 958px without scrolling... why force us to have a left admin sidebar?