Here's the real reason Windows didn't just switch every app over to the new style open/save dialogs automatically: a large number of apps hacked these dialogs t

Here's the real reason Windows didn't just switch every app over to the new style open/save dialogs automatically: a large number of apps hacked these dialogs to add extra controls to them. It was very common to see a file open/save dialog with some checkboxes or other options added at the bottom. This was easy to do: after opening the dialog but before it was displayed, you just walked through its child windows to add your own controls where you wanted them, and increased the dialog height to make room. But Windows didn't know you would be doing this until it was too late. The modifications were done after you called the Windows API to create the dialog. If it weren't for this compatibility issue, Microsoft would have been delighted to just replace the old dialogs with the new ones wholesale.