None of the carmakers do R+D on basic materials and are limited by the commercially available alloy formulas. If you believe that I have a bridge to sell you..

None of the carmakers do R+D on basic materials and are limited by the commercially available alloy formulas. If you believe that I have a bridge to sell you... Pretty much every traditional automaker spent more on R&D last year than Tesla made. Carmakers have tried unibody frames in the past, and they abandoned them pretty quickly because they're expensive to repair in the event of even minor accidents. (This is also why nobody else does shell cars like the Cybertruck anymore; because any damage to the shell can cause a structural weakness that would require the entire shell be replaced to make the car legally roadworthy.) With multi-part frames, individual parts of the frame can be made of different materials and stiffnesses based on the physics or safety requirements imposed on that part of the frame. This means that the overall frame can be both stronger and lighter. With a unibody frame, you have to use the same material through the frame, and the only way to adjust stiffness in any part is to control the amount of material used.