The electrical characteristics of headphones are important for two reasons, they determine how loud the headphones can be and if you have enough volume in a given situation-Impedance, sensitivity to sound signals from an amplifier (sensitivity) determines both these factors:
lower impedance means louder output but less tolerance on what your amp is capable off; higher impedances require more drive level before being audible with any kind or quality audio equipment due to its increased efficiency at converting electricity directly into voices while also needing better-nae such things as good cans/ear cups so we don’t miss much detail when listening