1. Probably passing thieves, so would drink the stuff not put it in the nice new Merc.
2.
This is an interesting point. Although it would be unfair for SAC to be caught because of the actions of a bunch of thieving t'rags, aircraft owners normally appear to suffer a continual risk of their aircraft being taken from them (lien) if they do not pay their bills for landing etc. Thus if you pay for the service, what duty does the airfield have in exchange for the landing fee?