Presumably, YouTube is merely a distribution point for those amongst us who would make local copies for redundant archival purposes.
I realize perhaps the intention of uploading to YouTube was more to advertise this project, rather than actually archiving it.
Distribution should be done via a website with links to files, e.g. ESO's gigapixel mosaic of the central parts of the Milky Way, a full size of 24.6 GiB [1]
Unless it is licensed under Creative Commons, in which case they themselves provide a download button.
Vimeo specifically has an option for allowing the viewer to download the video. I use this frequently when sending videos to clients. They can download the original file, and I don't have to use dropbox. Win-win