Why is there the message '!Do not use this registry key' in the registry?

Under Software\Microsoft\Windows\Current­Version\Explorer\Shell Folders, there is a message to registry snoopers: The first value is called "!Do not use this registry key" and the associated data is the message "Use the SH­Get­Folder­Path or SH­Get­Known­Folder­Path function instead." I added that message.The long and sad story of the Shell Folders key explains that the registry key exists only