Checking for changes before selecting a different node

Why do you need to ask the user if they want to save their changes when changing nodes?  Why can't the fact that the Save icon is enabled be a sufficient reminder, as well as when the application is closed the user will be prompted if they want to save their changes before closing?  Or why not display a pop up asking if they want to save their changes instead of automatically adding the cookie to the instanceContent.  If they say yes then save the results; otherwise throw the changes away.