How is Youtube different than that? In fact, why do people, even many developers, use CMSes? Most people like a management UI, the ability to easily upload from a multitude of devices, and all the other things that a dynamic app can give you. MediaGoblin also transcodes uploaded files automatically to be playable with common HTML5 media players. There's also federated commenting and following infrastructure in development.

You try setting up your system and inviting your family and friends to use it. People can use a MediaGoblin instance that you set up for them without much effort, with no additional software, and with a fairly decent user experience.