SteamOS started as an experiment by Valve to relieve their dependence on Windows as a platform to distribute their games. With the history of anti-competitive behavior by Microsoft in the past and the introduction of various Microsoft software stores, Valve sought to ensure that an alternative platform for distribution was available to Steam. Using Linux as a base, Valve began investing in improving the components of Linux that were required to provide an adequate or improved alternative to Windows for gaming.
Initially, SteamOS was launched with a category of products (with the assistance of third-party OEMs) known as Steam Machines. However, SteamOS was still too unpolished to provide a meaningful experience to users in a form-factor that traditionally favored the Windows operating system.
Big picture, a feature that was not exclusive to the SteamOS platform, was also available to the Windows Steam client. As a result, several OEMs ditched SteamOS for Windows and began marketing these systems as Steam Machines. Despite the failure of SteamOS on Steam Machines, Valve continued to invest in improving the SteamOS experience; hiring companies to work on the open-source software that would enhance the performance and compatibility of games running on SteamOS.