What is the stated purpose of the white tip on a Beagle's tail, known as the *flag*?

Answer

To make it visible when the dog’s head is down following a scent trail

The tail should be tipped with white, known as the *flag*, which serves the practical purpose of making it visible when the dog’s head is down following a scent trail.

What is the stated purpose of the white tip on a Beagle's tail, known as the *flag*?
animalclassificationDogbreedBeagle