Why? As long as you're not getting the ARM ones, you can stick on 10.15 - which is something many will do anyway for at least a year until Apple irons out the worst bugs of BS.
Only thing I'm still pissed about 10.15 is that Wine still can't run 32-bit apps.
You can stay on an older version for a little while, maybe a year at most until it stops getting patches. Then you get to make the choice of using an OS that's vulnerable to exploits and an OS with a gigantic backdoor in it.
Ah excuse me for that. 2 years of additional lifespan is still painfully short for a deprecated OS. Even free OSes like Ubuntu LTS get more years of support than versions of macOS (Ubuntu LTS release cycle of 2 years minus 5 years of support = 3 years of additional support after deprecation).
Only thing I'm still pissed about 10.15 is that Wine still can't run 32-bit apps.