Any boxing experts, I have a question

[SeeSon]

I have never boxed before, I am just a fan but I was having a conversation with a friend about that style Mayweather uses. My question is this. Why don't opponents just repeatedly hit him in his left shoulder and arm until it was in so much pain he no longer wanted to take shots there and changed up his style? It may be a dumb question as I confess I have never boxed before and it may not be possible, but I was just wondering so if anyone could humor me, I would appreciate that.

[Radium]

Shoulder ROLL

try hitting something that is moving away from you. The impact is completely reduced because its force doesn't have a clean and flush surface to distribute itself into.