Because not that many people build a gaming PC literally only for gaming. Likely it'll be used for other things too. Mine was built for gaming (replacing a laptop), but still needs to handle ripping my blurays and editing my photos
True, but I still wouldn't call a Blu-Ray drive essential. I have one, and I barely use it--actually playing Blu-Rays on a Windows PC is an awful experience because of bizarre DRM requirements like not allowing second monitors if they're too old (I have to unplug my second monitor to get anything to play) and reverting to a non-Aero desktop rendering mode because reasons. Plus you have to use proprietary software; VLC and MPC don't work. (You CAN make all these requirements go away with certain pieces of software, but it's a pain to have to get this stuff and I don't actually know how legal it is, though ethically I see absolutely nothing wrong with it).
Ripping Blu-Rays, sure, I can see being a thing, but I don't know how common that sort of thing is nowadays when most people are satisfied with Netflix or download pirated movies. Burning Blu-Rays I don't think is particularly widespread just because of the cost of blank media. Once you've got those uses out of the way, what's left? No software comes on Blu-Rays, really.
Anyways, to bring this back on-topic: finally I have definitive numbers on how much of an upgrade a GTX 970 would be over my current Radeon 6950. Almost three times the performance is probably an okay reason to spend more than my usual $200-250 sweet spot. Also a good sign that the DF article doesn't note any particular glitches or instability on PC.
Finally, it's amazing that this is the first time I learned that MONOLITH is behind this game. Lithtech lives!