To keep people from going to other video hosts who offer those features. It's a value-add for the platform. It lets you upload videos well in advance of publish

To keep people from going to other video hosts who offer those features. It's a value-add for the platform. It lets you upload videos well in advance of publishing them, or temporarily remove them. You also have to consider the fact viewer numbers are so low for private and unlisted videos they may as well be free to host, aside from the drive space they occupy.