Wait, why not just have your users upload videos to you, you automate the process of adding in a preroll, and then you upload this video to youtube on behalf of

Wait, why not just have your users upload videos to you, you automate the process of adding in a preroll, and then you upload this video to youtube on behalf of the user. I don't know much about youtube, but this solution seems too easy for it to be applicable. Why not?