With the Mac, a lot of people (i.e. me) will have the Dock in the way when you drag off screen: keeping the window buttons onscreen wouldn't help much, since th

With the Mac, a lot of people (i.e. me) will have the Dock in the way when you drag off screen: keeping the window buttons onscreen wouldn't help much, since they'd be behind the Dock, and sliding the buttons to keep outside the Dock area would probably be too weird-looking.