1. Run the gnome desktop 2. Create a new terminal window 3. Click on the 'edit' menubar item 4. Notice that there is only the single choice, 'paste'. Of itself, this has no value, since there is no accompanying 'cut' or 'copy' choice to allow any selection of text to subsequently paste.
This is how the X selection mechanism works - when you select something, it is instantly pasteable. No need for cut/copy (and cut makes no sense for gnome-terminal).