Because they're different use cases. Carbon-14 dating is useless for dating anything beyond about 50,000 years because it has a relatively short half life. It's generally used to date organic artifacts, and they won't all accumulate it at the same rate during their lifetime. There are many more variables and unknowns is some use cases than in others.
The "simplification technique" from the PsyOps manual seems to be heavily relied on by whoever you're getting your information from.
No one mentioned C14. I fully understand the limits of C14.
From that chart I gave you, from a university source, the other isotopes can be used to date “to the origin of the earth”.
U238->lead207
U235->lead206
Rubidium-87->Strontium-87
Potassium-40->Argon-40
See? No carbon 14, and no accusatory namecalling, OK?