Because as a developer, it's often easier to develop for Linux than other major platforms. You often get Linux compatability for "free". It's worth asking for for this reason.
That's not exactly true. With some newer tools, it's possible to export to an OpenGL Linux executable, but in other tools, especially older ones, it's still so specialized for DirectX that's it's not always possible especially with AAA games, and companies don't have much incentive to make Linux versions because the market share is significantly lower than Windows. The only reason that it's more easily possible with game platforms like Sony and Nintendo's hardware offerings (MS uses a special flavor DirectX for Xbox) is that the two aforementioned companies plus a lot of other game dev companies pour a lot of money into developer resources that Linux distros doesn't have.
You mean to say they put resources into lock-in to tax cross platform development. Those who care about the progress of the industry put resources into shared technologies like Vulkan, which makes cross platform development more affordable.
Yes, some do development in OpenGL, but why would a big company put resources in the development of something unless it has tangible benefits for the company? E.g. why would a big AAA company like EA put effort into changing their tooling to support OpenGL when they make millions from consoles and PC? It would only make sense to develop for non-DirectX or change tooling if the cost of changing is outweighed by the benefit. It's the same reason why a team like Github took 2 years to change from Rails 2.3 to 3 even though 4 had already been released for a while by that point.
I'm not saying it's right, and I wouldn't mind seeing better gaming support on Linux and Mac, but I'm saying it's reality.
Asking common sense questions about practices of legacy publishers is a futile endeavor. I stopped asking such questions for a while already. Those who want to innovate, do it, and find it useful for them. Size of the budget has nothing to do with interest to release for Linux and have wider cross platform reach. If anything, big publishers have more resources to do it. At the same time, innovators happen to be smaller studios, who actually are expanding Linux gaming market, while legacy publishers don't pay attention.
So what if it's new? Technology shouldn't stand in one place. MS got so scared of it, that they rushed to push their NIH lock-in alternative (DX12). It demonstrates they understand the strong potential of competition here.
Drivers can be busted anywhere (including Windows). But with Vulkan they are reduced to hardware layer which is ironed out rather fast normally. Not sure what you mean about OS integration (sounds too vague). Fullscreen, input and etc. are mostly issues related to X11, which should be cleaner with Wayland usage. The later takes longer than it should to get adopted, but all major DEs are already close to it.
Sound - never had any sound problems on Linux for a while. Are you sure you aren't measuring it by experiences of some early broken Pulse releases?
> never had any sound problems on Linux for a while.
User experience is not the same as developer experience. Debian (where Pulse seems mostly standard) is not the only distro. Vulkan is expensive, time consuming and difficult to develop against - for a game that already had multiple launch delays.