Patriarch Calcetti asked in defiance, "So what if I gave him a third rank weapon? Is it against the rules? What right do you have to claim that I cheated if the sects are fine with it?"
Then he shot back, "If you have to blame someone, then you can only blame yourself for not giving the children of your family third-rank weapons or blame your children for not being able to use third-rank weapons."
No one would give children at the first mortal coil third rank weapons to use even if they have it because those children wouldn't be able to use it.
Even Arthur, despite his great strength, still can't use a third rank weapon. He doesn't have life force to enhance the power of the arrow or divine sense to animate the arrow and lock onto a target. The best he can do with the bow is to use brute force.