Kevlar is nick/abrasion vulnerable and susceptible to UV degradation. It was tried on sport parachute suspension lines some years ago and proved not so good in the field for main parachutes, so people went back to spectra/Dacron when the kevlar lines started failing. You still see it occasionally on suspension lines for reserves, but they're generally not exposed to UV other than when deployed or a scheduled periodic repack and remain packed and unstressed for months/years at a time.