Pruning is necessary for alot of reasons. For safety removing dead branches that may fall could prevent damages or injury. Removing dead and/or damaged branches will also help prevent insects and other organisms from entering the tree. For health reasons it will prevent the tree from spreading disease. Thinning the crown will allow air to flow to the top of the tree putting less pressure on the root system. Proper pruning procedure will help maintain a strong tree structure, stability and help prevent any hazardous situations. "BAD" pruning may result in decaying.