We need a bigger battery for the same reason the Roadster has it: better performance. Voltage dropoff happens much later, and cooling is much easier. We may not use the range often, but that is a nice side effect of having a performance car that has unbeatable track performance. It's what a Tesla deserves. Plus, Tesla has always led the industry - as other manufacturers are pushing into larger, realistic battery pack capacities, Tesla can continue to push them to do better until there is literally no reason anyone would want an ICE vehicle any more. Range is as a boogeyman fear for newcomers, but it's a big one.