Yes, "just". DXVK as well as WineD3D try to support any game, even those who have native Linux versions. There were games in the past who dropped their Linux port (Rocket League), so it makes somewhat sense. There are/were also games who did not have cross platform multiplayer and you’d need to play the Windows version if you wanted to play with Windows gamers. Generally WineD3D (OpenGL, Vulkan) and DXVK (Vulkan) aren’t a Linux specific things, they just translate from Direct3D to OpenGL/Vulkan running on Wine, but that would work on Windows/ReactOS as well. Windows has OpenGL/Vulkan support. There are already Windows gamers who use such translation layers to play older games if it works better than Windows’ built-in backward compatibility. Even if OpenGL gets dropped by GPU drivers and even though Vulkan isn’t backwards compatible to OpenGL, it’s possible to write general OpenGL drivers who use Vulkan instead of implementing it per GPU. But another possibility would be to play a game that just has Direct3D/OpenGL support on Vulkan-only device with a translation layer like DXVK. Another factor would be games who have incomplete ports or simply games who have buggy ports.

It has a Linux Build, yeah