YouTube is the only large player on the social / media content currently offering services live streaming at resolutions 4K.
So far, Facebook offers the opportunity live video streaming to resolutions720p HDTV. It is true that this is not a low resolution, but user requirements and increasing development of smart TVs 4K requires new standards of quality video.
Starting from Friday, April 7 2017, Facebook launched in most European countries, 4K Live Streaming service.
Celebrities, companies, bloggers and other media who wish to share live images on Facebook accounts, I can do Friday at resolutions of 4K.
A very important step for Facebook, which every month bring improvements and new options for application both iOS and Android mobile devices, and Web version of the platform.