Forgiveness if this has been satisfactorily answered before

but I don't understand: Why/how are buyers allowed to give a Detailed Seller Rating to shipping costs when I do not charge handling fees?

I'm not trying to be snarky, I'm legitimately confused. My procedure: I photograph and package up a given auction item. I then list it, and in the listing I enter in the package weight & size dimensions. Once the item sells, I purchase the postage through eBay - the exact rate that the buyer is paying for the postage. I make no money off postage and I do not charge any additional fees (although I probably should for my time and materials).

If this is the case, why am I being rated at all when it comes to shipping rates? Shouldn't the buyer be rating the United States Postal Service?

Obviously I'm asking this because I'm projected to be "Above Standard" rather than "Top Rated" due to only one section - you guessed it, The Shipping & Handling Charges section.