Storing and renaming files from watched directory

I have a watched directory on Mendeley Desktop. When I move a file into this directory, Mendeley automatically recognises it and includes it in the database. However, it does not make a copy of it in the Local Mendeley directory, instead maintaining the link only to the file in the watched directory. If I were to then delete the file from the watched directory, it obviously loses the pdf. Why is Mendeley not making a copy in the Local directory, renaming it in the usual format etc. so that I don't need to maintain the linked paper in my watched directory?