Why not, because I would be concerned about the possibility of only getting $1 back in a dispute.

In PP dispute they refund full payment postage included, so that argument does not stack.

In any case, I only charge the actual postage on most of my items; if I decide to pay the insurance I do not charge the buyer for it.  I also cover the cost of packaging materials; if I can I use recycled boxes and bubble wrap, but I also have boxes I have paid for, as well as large roll of bubble wrap.  My FVF take huge chunk out of my profit.

So, excuse me, if I am not happy to see people who tripple their postage costs, to reduce their FVFs.