What is the primary reason for using anhedral on some aircraft?

The primary reason for using anhedral on some aircraft is related to decreasing stability, which can enhance performance. Anhedral is the downward angle of the wings relative to the horizontal plane. By incorporating anhedral, designers can intentionally reduce the aircraft's lateral stability. This reduction is beneficial in certain high-performance aircraft, allowing for quicker and more responsive roll rates, particularly in maneuvers that require agility, such as aerobatics or combat situations.

In this context, a decrease in stability can improve the handling characteristics when precise and rapid changes in direction are necessary. It is important to note that while this design can reduce stability, it doesn't mean that the aircraft becomes unsafe; rather, it is a calculated trade-off for increased maneuverability in specific flight scenarios.