Well PC games globally are not chump change. But no, while they can kill two birds in one shot, Xbox game + PC port, they have little motivation.It looks like Epic is itching for new consoles to finally come out as well. These current consoles have been out far too long now and are really holding back progress. As great as our PCs are, unfortunately, they are not mainstream and these devs sadly won't deliver more graphically intensive games until the consoles can catch up as well with all their mainstream-ness.
But another reason is that Microsoft controls PC gaming via DirectX. They can stifle PC gaming by sandbagging new DirectX features. Because PC graphics growth is as much about new features and software optimization as pure horsepower. Without the software meeting the new hardware, growth is limited.
It will probably be to daunting but I would hope that Steam is successful in porting Steamworks to Linux and resurrects OpenGL for everyone in the process.