I don't think that's it. Games also need to run on consoles, mobile phones, and sometimes web browsers. Cross platform development isn't a new concept in game development, and all major commercial game engines work on Linux (well, they do today at least)
Most software used in the VFX industry does officially support Linux, and a lot of those tools are also used in game dev. Maybe Unity and Unreal's Linux support hasn't been great, and that's the only reason?
I guess it's easier to get into gamedev than VFX as an indie, and if you have little/no technical background then there's a good chance you're on Windows or Mac when you start looking up Unity/Unreal/etc tutorials, and then you just stick with what you know.
Most software used in the VFX industry does officially support Linux, and a lot of those tools are also used in game dev. Maybe Unity and Unreal's Linux support hasn't been great, and that's the only reason?
I guess it's easier to get into gamedev than VFX as an indie, and if you have little/no technical background then there's a good chance you're on Windows or Mac when you start looking up Unity/Unreal/etc tutorials, and then you just stick with what you know.