Silo Thinking

Why don't more senior executives call the managers in their ranks when those managers engage in silo thinking? That question has puzzled me for some time. I think there are three reasons. First, some people shy away from the notion of calling a colleague selfish - they are simply too conflict averse to do it. Second, they worry about reciprocity. Will that manager call senior executives out for their own silo thinking? Third, some executives believe that some element of competition among various units is productive, but they have a hard time balancing the desire for competition with the need for collaboration.