In 6 trips to Africa, I've never had a rifle pointed at me, either by a PH, a tracker, another hunter, or a game scout. They are all very conscious of where rifles are pointed at all times.
They carry them that way because they don't use slings for safety's sake. When you are hunting where dangerous animals roam, you don't want anything (i.e. sling) that might catch on a wait-a-bit thorn or any other ground flora. Another reason you will never see a PH's rifle with a scope.
Try walking 10-12 hours a day, and see if you don't carry a rifle on your shoulders occasionally. Most of the time, they are carried in their hands - sometimes on the shoulder. A typical PH can care less if he looks cool - sheesh.
