That doesn't sound like what I call an "ability", but rather a perk, as it involved absolutely nothing on your part, and therefore does not contribute much in making your experience more interesting. It also sounds very infrequent.
Pretty much, so far as I can see it is an incentive to compensate the trader somewhat for the extra cost associated with longer trips. Of course if the profit off the food isn't good enough for the trip, or some incentive isn't in place from a realm, why the hell are you bothering.
