Serious question, not trolling: Do a lot of people just upgrade for the sake of upgrading/to have a newer/larger number in their PC? 😛
A 25-28% faster 880Ti does nothing to fix the situation where we need more GPU power. Conversely, for 1080P, 780Ti slices through mostly everything else. That's why I just can't get excited even if the 880Ti is 28% faster for $550 over 780Ti.
For power users on 1440/1600P, 15-30% is still not good enough. For a real game changer beyond 290X/780Ti, we need 50-100% faster to make the gaming experience significantly better.