Most likely you will need more than just your ski jacket pockets to store things when you are heading into the backcountry. In face you should really have an avalanche transceiver, shovel and probe before you even think of skiing off piste. But the other advantages of wearing a ski backpack are that you have a place to store extra layers, food, water and any other things that you might deem essential.
Luckily Snowleader has a great selection of ski backpack and snowboard backpack from the industries leading brands - Black Diamond, Dakine, Picture Organic Clothing, Arva, Ortovox and more