Funny thing is, here we are talking about these mega-pixel monitors when the most common screen resolution (at +- 31%) is... 1366x768.
Immediately followed by 1920x1080 for 21.5% of users out there.
Only 0.11% are blessed with 4K monitors (3840x2160).
The "most common" anything often isn't relevant to understanding. If you looked at most sold phone models then you wouldn't even get a smartphone in the top 10. But somehow the mobile game market targeting smartphones has grown into a 25 billion dollar industry.
And anyway let's not forget that there are plenty of gamers that are opting for lower resolution but higher refresh rates. And then there's another (much smaller segment) opting for G-sync or Freesync screens. Etc.
I was going to question how Frogboy manages to run Ashes at 5k when I can't even run it at 60fps in 4k with the same GPU... but it seems there's been a ton of optimizations since I last played it! I was averaging ~30 fps at 2560x1600 last time, now I'm getting almost 55 fps at 4k. I'm guessing my 8gb memory and 4690k cpu is dragging me down a bit.