Chemo shrinkage and MX

Hello
I wonder if someone can help with this question
I have had 3 EC and 3 TAX. My surgeon feels it beneficial to have 2 more TAX, (which I was not expecting) to further shrink the lump (5cm) I have agreed to this.
My question is why does the lump need futher attempts at reduction when I am told it 100% has to be a mastectomy, In other words it is coming off anyway, so what is the point?
Thanks
WS

I think it’s easier to get clear margins.