It’s for their matchmaking service. You can of course use your own solution.
But this seems to be one of the issues with Unity right now. They use a lot of resources for non-core systems, that although nice to have can’t compete with dedicated solutions. At the same time there are large problems with the basics of the engine.
They will have to decide if they want to focus on the hobbyists and low end indies with stuff like simplified source control or compete with Unreal as a high end enigine with PBR and global illumination.