It's just development resources. Very few people not only have the right video card (need HDMI 2.0a + HDCP 2.2) but also a 2015 or 2016 4k TV with HDR10 implementation. That limits it to the 950/960, 1060, 1070, 1080, Titan X Pascal and AMD 470/480 for the most part plus a TV that supports HDR10 properly in PC mode at 60 Hz. It sucks, but even the GOW4 developers said they aren't implementing PC HDR unless there is big demand for it and the GOW4 port looks really well done. Supposedly all Maxwell cards "support" HDR but there aren't any HDR monitors so that limits it to cards with full HDMI2.0a/HDCP 2.2 support to connect to 4k TVs.