20% is not enough of a reason for me (as a casual user) to upgrade my M1 Mac Studio Ultra to an M2 Mac Studio Ultra but I can see why businesses may well consider if if they can complete tasks 20% faster. Time is money and it won't take long to recuperate the cost of upgrading.
No one ever upgrades one generation. You keep the computer 3 to 5 years then buy whatever is available at that time. Perhaps you g from an M1 to an M3 or M4.
It is the same with cell phones, very few people buy a new phone every year.
As for businesses, there is a 3-year period for capital depreciation. You can't write it off in only one year.
Apple does not bring out these new products every year hoping people will trade in one year old computers, there are plenty of people with Macs from 2019 and even older and also new customers
Finally, even if the new Mac is 20% faster, the job you are doing will not be done 20% faster. For example, the above text I just typed would take just as long if I used a new Mac Studio or my old 2014 Mac Mini.
Mostly what our Macs do is wait for the user to move the mouse or type the next character. Look at "activity meter", mostly you see the CPU is sleeping, even if you have 15 browser windows open.
A faster CPU only helps when you do some compute-intensive task where yu have to wait and can do nothing productive while waiting. Mostly this happens if you do media editing but sometimes also some kinds of engineering tasks. But even when I use 3D CAD, I only have to wait for the computer now and then, maybe for a render to complete. Mostly the computer is waiting for me to do something.
