Rejuvenating old shrubs is a challenging pruning project. A sparse or overgrown hedge can be rejuvenated by pruning back in late winter. Improving appearance is a legitimate reason to prune. Suckers at the base of a shrub are ugly and should be removed. Avoiding injury or damage by pruning is wise maintenance.
Low branches can damage cars, poke people in the eye or be a hazard for the person mowing the lawn.
Limbs hanging over utility lines, the house or other valuable property can be a liability. Flowering and fruiting can be controlled by pruning. Flower buds can be removed to encourage more vegetative growth. Pruning can be used to stimulate flowering on some plants like wisteria and lilac. Selectively removing some flowers will result in others being larger or producing larger fruit.