Rifle rounds punch Kevlar like butter. Need Level IV rifle-rated plate armor to stop a battle rifle round. Even then, it only covers the pumphouse, the neck, head, pelvis and great arteries of the arms and legs are also exposed. If you're being shot at by a rifle, you have very big problems. There's a reason over 3 centuries have gone by and all the militaries of the world still use them. They work extremely well at their task.
Likewise. More to spread out the backface deformation from a rated threat (pistol/shotgun). Rifles were going to be problem regardless for IIIA vests, shockplate or not.