There’s a reason most gamers turn to Windows as their operating system of choice, and that reason is DirectX. DirectX is a proprietary graphics, sound, and input API developed by Microsoft, and has never enjoyed official support on Linux. (Support for DirectX 9 and 11 exists through WINE, but stability and speed can be spotty.)
Vulkan is a new cross-platform API that is the descendant of OpenGL. Even though Vulkan is still young, developers of the API are working on Vulkan Next, which will be the, well, next version of Vulkan with increased support for virtual-reality, multiple-GPU gaming PCs that use AMD’s Crossfire or Nvidia’s SLI. Valve’s Linux-based SteamOS added support for Vulkan in February.
As for adopotion of Linux-based gaming on Steam, there were mixed results. The Steam Hardware Survey showed a drop in the percentage of users using Linux. However, the total number of Steam users has expaneded rapidly, and so has the total number of Linux users along with it. (It’s also interesting to note that the Steam Hardware Survey did not list SteamOS as a Linux installation.)
Even with support for Linux gaming gaining a bit of steam, developers didn’t deliver on promises to release big titles like Batman: Arkham Knight and The Witcher 3: Wild Hunt to Linux. Linux, it seems, still suffers from a chicken-or-egg problem when it comes to games: Developers won’t make games unless there’s a big enough audience, and there won’t be a big enough audience until the games are available for Linux.