The answer is clear. The main probably only perpertrators of this practice are nationals and it is one of the ways that they can try and impose themselves on you as an expat - it manifests itself in many ways on the road.... it is because in general they are incapable of imposing themselves on expats in any other way - socially, professionally, personally, culturally .....its a social inadequacy that one gets used too. In general the advice is ignore - they know no better.