What would you rather be, a team player or a do-everything-on-your-own individualist, that is the question. If you had a multi-faceted job at hand, what would you rather prefer to do? Some people would want to do everything by themselves and would give up control only under duress or extreme fatigue or when they finally realize that they need more resources than they themselves can muster.
Delegating responsibility is a management technique for not just businesses but also mundane day to day affairs as well as in organizing elaborate social functions. Including people in the decision making process and providing them with information as it becomes available, gives them a stake in the affair and makes them a part of your team. Some people adopt the policy of disseminating information on a need to know basis. Unless there is a good reason to do so, withholding information and being secretive just leads to rumor-mongering and creates unnecessary animosity.
At times, this is just a result of the clash of strong egos. Perhaps you may be angry or hurt at somebody and you want to show them that you can manage without their help. But think about what this will mean in the long term. Side stepping anyone will make them feel left out and dejected. What you end up with is creating unnecessary grudges and further complicating your already mangled relationships.