The battery is already a huge chunk of the cost, the added benefit of putting traction on the trailer itself is pretty big and could theoretically allow trucks

The battery is already a huge chunk of the cost, the added benefit of putting traction on the trailer itself is pretty big and could theoretically allow trucks to exceed their rated towing capacity if regulators get on it. Also it means that it's compatible with ALL trucks, not just electric ones, and doesn't rely on truck manufacturers integrating a new standard power supply that can be used while the truck is moving.