If you have a machine with a GPU that can do 720p at 60 fps in a game, and a machine with a GPU that can do 4k at 60 fps in a game.....and you hook both machines up to a black and white TV from the 70's, you won't see a difference. 4k resolution becomes snake oil at that point, because no one can tell any difference when viewing both of the GPU's outputs on that TV.
The majority of gaming headsets and standard PC speakers are B&W TV's. I'm not surprised people can't hear a difference when using those things. Even the expensive gaming headsets. They make them look cool and fancy, but are using the same cheap, generic sound hardware all of them use. Now, as long as people are happy with what they have, that's perfectly fine.
When I was running a Logitech 2.1 speaker setup, I picked up a little Modi Multibit external DAC. I thought that I maybe could hear a difference between the DAC and MOBO sound. I think I did. Maybe. Then I replaced my Logitech speakers with a pair of Adam A5x powered speakers. The difference between my little Schitt DAC and the mobo onboard sound became apparent, then. Clarity, separation, soundstage, etc. were all better with the external DAC.
I suppose the moral of the story is that if you play a game locked at 720p 60 fps, then once you have a card that can do that..... other more powerful and more expensive GPUs seem stupid, since they look exactly the same locked at 720p 60fps.