Inconsistencies are another fun one.
Prior to Windows 95, the way to close a window was to double-click the top-left corner. Win 95 added a Close button to the top-right, but double-clicking the top left continued to work.
Windows 8, I think it was, removed the double-click option... but only when using apps built the "new way" (Metro). To this day, in some apps (e.g. Notepad and Paint) you can close from the left, in others (e.g. Maps and Settings) that'll maximise the window, and in others (Firefox) it'll open and close the File menu.