They lack rigidity in flat areas from the lack of contouring, so need to use a thicker gauge material to to keep panels stiff. You can even see the unintended curvature in the door panels
Elon Musk wondering why engineers use arches in construction and concluding it’s because they’re old-fashioned fuddy duddies
Yea, and also, like - the human eye is incredibly good at noticing any deviation from perfectly flat, especially if you’re talking about a semi-reflective bare-metal surface. Any little imperfection will immediately draw your eye because light bounces off it weird. There’s a reason every car manufacturer ever only evokes the sense of flatness, but usually incorporates some more complex bends, light lines, stuff that both serves stability functions, helps when the panel will inevitably contract or extend due to thermal differences annnnd makes you not see little imperfections in the geometry as easily.