Endurance racing, bikepacking, and epic rides place a premium on storage space. You end up stuffing your hydration packs, frame bags, and jersey pockets to the point that there's just no room for anything else. When the day starts to warm up, there's nowhere for you to quickly stow the layers you needed to get through those chilly morning miles. You end up cramming your arm warmers, jacket, vest, or cap in with your food and other essential gear, making it even harder to access what you need without slowing down or taking the risk of losing something important on the trail.