Why is low-stretch Spectra fibre used for power-kite flying lines?

In the context of modern kite sports, Spectra fibre is utilized for power-kite flying lines because it is a low-stretch synthetic yarn that possesses exceptional tensile strength.1

This combination of properties is essential for power flying, where kites act as high-performance traction engines capable of generating significant pulling power to propel vehicles across land, water, or snow. By minimizing stretch, these lines ensure that the pilot's control inputs are transmitted instantly and accurately to the kite, allowing for the precise maneuvering required to harness the wind's force effectively.1