Every author writes in his/her read-me file about sharing and re-uploading policy. Not everyone wants his/her files to be reuploaded elsewhere.
E.g. I've uploaded mine to ModDB, JKHub and Desura and I can watch its popularity, the number of views, downloads etc. And I don't want my work to be reuploaded elsewhere because it is not suitable for me. Moreover, most reuploaders doesn't even include author's name, source and readme in reuploaded file. Or even modifies them into some piece of garbage. Dat's not cool.