Accurate training datasets are essential to machine learning because the accuracy of your model depends on the quality of your data. Your model's performance will be limited by the accuracy and consistency of the dataset used to train it. Using inaccurate or inconsistent data can lead to poor model performance and, in some cases, make the model unusable. Therefore, ensuring the accuracy and consistency of your labeled data is essential to achieving the best possible model performance.
In a nutshell: more accurate datasets equals more precise ML models.