New
#11
It is used for old broken applications that hard code the paths from previous versions in Windows. For example, in Windows XP the directory you would be looking for is "C:\Documents and Settings\[username]\My Documents". But in Windows Vista/7 they changed the paths to "C:\Users\[username]\Documents". This has the side-effect of breaking those applications that hard coded the old path.
If directory aliases was not necessary, symlinks would not exist. Junctions is just a form of symlinks.