Originally Posted by flowers
It could also be because then the amount is non commisionable and they dont have to pay TAs on the extra amount. Taxes also they pay on the amount are affected.
Point well taken.
Reminds me of why a $1 item on eBay carries an inflated shipping charge... to avoid eBay service charges. However, for the fuel issue, it makes total sense to keep them separate, since they can fluctuate.