This is only because it is well calibrated with objects of known age.
Example: wood found in a grave of known age by historically reliable documents is the standard for that time for the C14 content.
Archaeologists have long used carbon-14 dating (also known as radiocarbon dating) to estimate the age of certain objects.
After all, this what the archeologist guessed in their published books.
A man called Willard F Libby pioneered it at the University of Chicago in the 50's. This is now the most widely used method of age estimation in the field of archaeology.
by Helen Fryman Question: What about radiocarbon dating? Response: I asked several people who know about this field. (1.) C14 dating is very accurate for wood used up to about 4,000 years ago.
In this interactive, learn how radiocarbon dating works, what it takes to determine a date in the lab, and why it's challenging to pinpoint a date precisely.
Radio carbon dating determines the age of ancient objects by means of measuring the amount of carbon-14 there is left in an object.
The methodology is quite accurate, but dendrochronology supposedly shows that the C14 dates go off because of changes in the equilibrium over time, and that the older the dates the larger the error.