Why is carbon dating often considered inaccurate in determining the age of archaeological artifacts?

Carbon dating is often considered inaccurate in determining the age of archaeological artifacts because it relies on the assumption that the amount of carbon-14 in the atmosphere has remained constant over time, which may not always be the case due to factors like changes in the Earth's magnetic field or human activities. Additionally, contamination or mixing of different carbon sources can also affect the accuracy of carbon dating results.