I have a few thoughts on this, and I'm glad there is a thread for this.
Firstly:
Forget about the PC Master Race versus Console peasant battles; the fact of the matter is that the majority of gamers out in the world are not on Reddit of forums all the time, so they could not care less for any of this master race bullshit. The bulk of paying gamers are people that buy games to play them on a platform that is the most cost effective for them. Most people don't care about shiny graphics and buy games because of either hype, marketing or word of mouth. This is the reason why games spend half of their production budget on marketing and PR. It's not to satisfy the hardcore gamer group, it's to entice the biggest market share of gamers, because there is where the biggest profit margins lie. It seems that most of these types of gamers are more prolific on console platforms like the Xbox One and Playstation 4. Just look at the number of consoles sold to date of both; they easily match if not surpass the number of active Steam accounts in the world.
So, gaming companies has to worry about their bottom line, otherwise they will go out of business, and the smartest and best business decision is to focus all your attention to the biggest group of your target market. It's called market segmentation, and every single business worth it's salt will be extremely aware of these numbers. This is why, no matter what, console gaming will always be first priority from a business perspective, as it is where the most money is.
Secondly:
To optimize a game for console platforms are much easier than it is for PC; you only have one system to optimize for, where PC game development must encompass all possible types of PC configurations. Also, look at the Steam average gaming PC. Are these the type of PC's you'd expect to run games at super-ultra-maximun graphic settings? No, it's not. So why spend millions of dollars developing a game that not only a small amount of gamers can enjoy fully, but only a smaller still amount to enjoy to the fullest? When business decisions are made to ensure costs are minimal and profits are greatest, you will have to make sure you develop for the biggest share of people. Not everyone is sporting a 980X or equivalent card, and they are more than aware of this fact, and is more than happy of playing a game at much lower settings. So as a developer you make sure you optimize your game that the average gamer can still enjoy as much graphical fidelity as possible, This always leads to cutting edge graphics being "downgraded" to ensure the game can run on as many PC's as possible.