Exactly, its not always about whether the machine is simply 'enough'. These products arent cheap and will last an average consumer 5-8 years so why wouldnt you want the latest and greatest especially when the 8th gen CPUs are the biggest updates for apple hardware since 2012... it can literally be a 50% performance increase.
So my question is why would you buy old hardware... for many it wont be a new purchase it will be replacing an older piece of apple hardware, unless its bricked or has died then most can probably wait, if you cant then I suppose the iMac pro is an option. iMacs are more niche than Macbook pros I would speculate the majority of people purchasing would be upgrading not buying for the first time.
I think you’re missing the part about work that the previous poster mentioned. For some it really isn’t an option to wait. My 4K iMac arrived today, I had waited and waited for a new model and I can’t afford to wait any longer because my job is 100% home based and I work solely through my computer.
For a regular consumer, sure no rush just wait for the next one.
For me and many others it is different. I bought the 4K iMac this week because I can’t wait any longer. At the same time, because it is my work machine I may just buy the latest one whenever it does release too. It’s just a different set of needs.
Edit: Also, from the work perspective it is a little tedious when searching threads and seeing a slew of “Wait for the new one” instead of actual advice. I’ve been seeing that a lot this week while researching mine lol