For two reasons,
First; If the quarter rib had been machined any lower, the release levers for the QRW scope mounts would hit the barrel, making removal much too slow.
Second; I am 6'10"(208cm) tall. The higher rib is MUCH quicker for me to use. When I throw this rifle to my shoulder, eyes closed, then open my eyes, I'm looking right through the scope and dead on target. It's about practicality for me, rather than looks!