>according to an set of rules the user can't be expected to know This is consistent, it's just never properly communicated. If the source and destination are

>according to an set of rules the user can't be expected to know This is consistent, it's just never properly communicated. If the source and destination are on the same drive, dragging executes a move by default; if the source and destination are on different drives, dragging makes a copy by default. macOS has this problem too, where you just flat out can't cut/copy/move files with the same shortcuts and verbiage you'd use for text (or the option in the menu is greyed out for no reason).