Before the benevolent guvment CPSC decreed that all protrusions on a bike had to be snag/slice/cut proof QR levers were straight, not curved. Racers made sure that they were closed in a direction that would minimize the possibility of them collecting spokes if they contacted another rider’s wheel. As your front would likely contact a rear and your rear another’s front, front skewers were parallel to the fork blade or upward. Rears were tucked down and forward. Curved levers made it less likely untimely spoke removal would occur and the shape is easier on the hands.