Wait. What? The only game on the PS4 (that’s I’m aware of) that didn’t run in true HD was Battlefield 4 (which was upscaled from 900p). Everything else runs at a full 1080p.
The Xbox One is the only current-gen system that has had difficulty in this area.

My guess, is that it has everything to do with bringing the hardware up to a level that will work optimally with the PlayStation VR (ensuring that it can easily render two, 1080p scenes simultaneously, with the option of rendering other scenes directly to the TV at the same time).
The 4k TV support is just gravy on top.
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