What is the rational in considering the opinion of the people who may get affected when formulating a strategy over an issue?

Opinion of people is valuable if the strategy is formulated.  Insights can be discovered and it can give you a holistic view of the situation.  This is good if the person move up or change roles which he requests or wants.

However, if the person will be affected negative, care must be exercise as this may demoralise the person.