I was motivated to upgrade because of content creation. I needed more performance to support greater levels of 3D subdivision and more complex game engine editor worlds. A lot of other people are pushed to upgrade by VR, buying higher-resolution or refresh rate monitors, or wanting more visual eye candy in their games. For some people, Half Life Alyx and the Valve Index were Crysis-like motivations to upgrade. Otherwise, there's been a lack of games that actually require something newer than a 9 or 10-series GPU.
I don't know that there's anything to support a 40-series upgrade right now. The price to performance ratio isn't worth it. Nvidia is probably happy that the 4080 isn't selling given that the 30-series cards have somehow increased in pricing recently based on other news posted on Tom's. The 4080 isn't cannibalizing 30-series sales right now. We can all sneer at Nvidia for their pricing and inventory, but I they likely planned for the 4080 to sit while 30-series gets cleaned out.