Difference between a Lapel Grasp Practice vs. Reality:

The karateka needs to understand that when we practice this technique it is done in the classical manner. When we practice the one hand lapel grasp it is to enable the opponent or tori to develop the mechanics of the technique. The reality is the opponent will be trying to strike you with their free hand or use it to break your balance, but the technique will still work. No one will simply grasp your garment.

When an attacker grasps your lapel or lapels, it is to control your movement. A judoka will be setting up a throw.  A street fighter will want to keep you in range so they can deliver a punch, knee, or elbow.