The removal of the factory-installed back seating in the Toyota GR Corolla is a modification undertaken to reduce vehicle weight and potentially improve performance characteristics. This modification often involves removing the seat assembly, including cushions, frames, and related hardware such as seatbelts. An example of this would be someone wanting to prep their vehicle for track days.
Significant weight reduction can improve acceleration, braking, and handling. Historically, this type of modification has been prevalent in motorsports and performance-oriented builds where every incremental gain in vehicle dynamics is crucial. Moreover, eliminating these components can free up space for aftermarket roll cages, racing harnesses, or auxiliary equipment.