This is also baffling. A button, a text input, a checkbox, a drop list, a combo - they all have a "default" look in every Windows version since 2.0 (1 didn't have the drop list, IIRC). It shouldn't be difficult to make an abstract description of a dialog box look at home with a new version of the OS and, yet, digging through Windows 10's built-in apps you sometimes find things that you recognize as skinned versions of Windows NT 4 dialogs. That they look like NT 4 dialogs with the Windows 7 skin applied is disconcerting, at best.
The Office team used to pioneer (hard-code) the look and feel for the UI, and then the Windows team goes and implement the look and feel system wide in a generic way. Then somewhere along the way, the Windows team decided to hard-code the look and feel that you could now do an archeological dig through decades of UI.
