Ahhh - OK, the blindness has left my eyes.
You want windows maximized *the first time* you run them. Now that I know that I can answer why it is not happening:
- The default size of windows is sometimes set as a maximum - think popups in Internet explorer - if you close all IE windows and then the popup last, chances are that IE will next open in a size that conforms to that last closed window. But since there is no default size if you've never opened a particular window, I think programmatically it starts out using a default size, which looking at things seems to be between 800 x 600 and 1024 x 768 (I have an onscreen ruler but am too lazy to check that).
- Some applications force a size until the user has said otherwise in their code - hence some really weird shapes for apps that open first time - and because some apps also look goo funky in full screen mode, I'd say that opening all windows in full screen mode can actually be a bad thing - especially a stay on top window that doesn't contain / has had removed the minimize and resize controls so it is either open or closed - imagine that - an application that is set to run on top of all other windows that opens maximized and that you can only get out of your way by closing - but that you in actuality need open and *not* maximized so as to refer to it with another window - without those minimize and resize controls, you're SOL....
(as another one of those annoyances along the same lines as yours - just a WTF kinda thing: I just spell checked my post, and the friggin word "resize" was not found in the dictionary and so Fx asked me to correct it....)