SteamOS Didn't Use Ubuntu Over Legal Issues
Last month when SteamOS was publicly made available in beta form there were many surprised that Valve based their Linux distribution off Debian rather than Ubuntu, which they had been heavily promoting up to this point for Linux gaming. There was some speculation why Valve went with Debian, but Gabe Newell has now confirmed the reasoning for not basing their operating system off Ubuntu.
Some speculated Valve went with Debian over Ubuntu due to not having to deal with the Mir Display Server, Canonical wanting to be paid for using Ubuntu Core, Valve not liking the direction of Ubuntu, etc. According to Gabe at yesterday's press conference, the reasoning for going with Debian over Ubuntu was simply described as "legal issues", according to our German friends at Heise.de.
We also have earlier coverage on Phoronix from the Valve CES 2014 press conference in SteamOS Update Now Officially Supports Intel and Valve Already Has A Dozen Steam Machine Partners. More SteamOS graphics/gaming performance benchmarks are also coming on Phoronix as soon as I return to the United States in a few days.