I think this comes down to market economics more than product design. Many manufacturers have been production limited by cell supply for a long time. You _could_ make cars with extra large battery packs for those who live in exceptionally cold climates, but it's a limited market, and you'd be taking away cells from shorter range models. E.g. you're likely to make more money selling 5 cars with a 60kwh pack than 3 cars with a 100kwh pack.