Playstation is based of FreeBSD and Android NDK has OpenGL ES, Vulkan, OpenSL ES, OpenMAX.
Porting is relatively easy for those studios, they don't because that development costs of having a Linux build and QA isn't worth it.
With Valve pushing WINE/Proton is even better, they don't need to care at all that Linux exists, Valve will do the work for free for them.
Which as IBM discovered, isn't really the future proofing way to build an ecosystem with someone's else OS.