Drawcord closures—those elastic cords with a toggle at the cuff—are all about sealing out deep snow. They're typically found on gauntlet-style gloves and mittens, which have a longer cuff that goes over your jacket sleeve. When you're skiing powder or heading into the backcountry, a quick pull on the drawcord cinches the cuff tight, keeping snow from sneaking in during a tumble or deep turns.
For most resort skiing on groomed runs, Velcro straps work perfectly fine and are the most common option you'll see. They're easy to adjust one-handed and keep things secure. But if you regularly find yourself in waist-deep snow or skinning up in the backcountry, drawcords are worth having. They create a more reliable seal around a bulky jacket sleeve than Velcro alone, and they're easy to operate with cold, gloved hands.
One thing to note: drawcord gauntlets add a bit of bulk, so if you prefer a low-profile fit or mostly ski spring conditions, you might find them unnecessary.