People have trees trimmed for a variety of reasons. We most often trim trees to thin them out and keep them healthy to last a lifetime. By thinning out the tree you create proper spacing, which in turn reduces overcrowding and relieves stress on the tree. Sometimes the tree just catches too much wind and puts the tree in jeopardy of coming down, thinning the tree out will let the wind pass through.
Another reason we trim trees is to keep branches away from the house and roofs. When the wind blows, not only do you hear a terrible noise but the branch can cause damage to the home.