Why doesn't the taskbar return to its original size when I return my settings to their original values?

Commenter Gareth asked why, when the system metrics change and the taskbar changes size to match, the taskbar doesn't return to its original size when the metrics return to their previous values. Because the taskbar doesn't remember the path of changes that led to its current state. It just knows its current state. Let's say the taskbar is 30 pi...