There’s a few places where losing a ski could at best ruin a run and at worst present a serious safety concern. I’ve had a few close calls with a rogue ski trying to start the descent without me, now I carry a simple leash all the time.
Two mini carabiners and four or five feet of p-cord does the trick. I keep it tucked into the camelback sleeve on the shoulder strap of my pack and don’t notice it’s there, but it’s handy when I need it. The leash usually gets utilized at the end of a bootpack, knife ridges, top of couloirs, etc. I clip the heel risers so it’s easier to unclip when I’m ready for the descent. Super simple and lightweight piece of equipment for security and peace of mind.