There are different objectives for tree pruning.
The first one is always safety. Trees in areas around your home or on properties where there is foot traffic or vehicles need to be pruned to remove deadwood. Dead limbs fall from trees frequently and should be removed to reduce liabilities with trees making areas safer. During this type of pruning, it also gives the arborist a chance to view the trees canopy (aerial assessment) to look for any types of stress cracks, hanging limbs, structural defects etc. Another safety issue involving tree pruning is to prune for any type of visual obstructions for traffic areas or low hanging limbs and foliage that people could walk into.
Secondly, trees should be pruned for maintenance concerns with homes and buildings. Limbs and foliage touching and rubbing can damage paint and excessive rubbing can even cause minor structural damage. They can also become an entry point for insects or even unwanted critters. Too much low canopy can start to encroach and present conditions favoring mold or mildew build up from poor air circulation and too much shade. Mosquitoes can also become more prevalent in this environment and fungal problems with trees and plants will become more likely. Thinning tree canopies may be necessary for added exposures to certain plantings or turf grasses.
Thirdly, trees may be pruned to promote overall health and to help encourage proper growth and structural integrity. Generally speaking, healthy trees have good foliage density but are not overcrowded in the interior. Crown thinning can help alleviate the wind sail effect. Trees with good symmetry and scaffold branch arrangement are typically stronger and less susceptible to storm damage. Dead limbs that are removed routinely and properly vs falling off on their own can prevent damaging wounds that can sometimes happen and lead to decay columns. Dead wood removal also eliminates the hosts for wood boring insects and some diseases. Trees in close proximity to one another often times start to conflict; pruning can helps keep separation between them. This helps maintain good air flow, sunlight, and symmetry in their crowns. Structural pruning could be done to help fruit trees withstand the added weight of the fruit.
Finally, trees are pruned for aesthetics. The purpose for this is to help embellish a property, adding curb appeal and accenting architectural features. Properties with poorly maintained trees and plants can detract from the beauty and make them feel less inviting and hospitable. Differentiation between trees and between trees and structures is welcoming and makes the overall look and feel of a property better. Vista pruning could be put into this section as well. This type of pruning is done to gain a sight line or improve a view, typically of a natural feature such as a lake, mountains, or golf course.