the traps are a much larger muscle group then most people think . most people think they are just the small muscle on top of your shoulders around your neck, but in reality they go half way down your back

they are a large and powerful muscle group.. most guys that are just average stregth level can rack pull 405 to hit traps. 315 shrugs are easy as well .. traps are very strong. so to hit those type of numbers every single day is going to cause a lot of fatigue. the STF, stimulus to fatigue ratio is going to be high towards fatigue.
now granite, you could lightly hit them every day . but you really think such a powerful and large muscle is going to respond that well to being hit "lightly"