Would be a good example if the requirements to run games did not increase with each passing month...
I mean, is it harder for a Porsche to overcome air resistance one day to the next? Or does the required power to turn a tire increase with every mile driven?
Whereas a Porsche is always overkill for driving around town, a graphics card eventually becomes useless as requirements for newer titles is always becoming more demanding.
The visuals you get from games is also constantly increasing. You can easily stick with the same hardware for several years, as long as you don't expect to get better visuals (you may need to use lower labeled graphical settings, but the visual quality should be similar). Though you likely will still get a little better visuals as Dev's get better at getting more out of the hardware.
The only reason you feel a need to buy new hardware, is because you feel a need to see the improved graphics.
It would be like needing to constantly upgrade your Porsche to compete in road races, because technology allows your competition to get faster, and you need to keep up.