This is a capability that's essential to an asset generation workflow. A simple example would be opening a 400 x 200 file and resizing it in one step to 200 x 100, scaling its contents and effects accordingly.
Illustrator doesn't handle this well at all. It will resize the artboard to fit its contents on double click (a useful feature, but not one that addresses the primary requirement to simply scale everything - if you want a margin around the contents you need to draw a transparent box). iDraw does much better with its Artwork Size dialog.
