There are two major reasons that trees, bushes and fruit trees to be pruned. Either it has become over grown, diseased &/or dead or as a preventative measure in avoiding potential issues in the future:
Formative pruning is the pruning of a young tree in order to produce a tree which in maturity will be free from major physical weakness. I.e. removal of competing leaders, crossing branches and weak branches.
Trees, bushes and fruit trees which have outgrown the garden they occupy and/or dead, diseased or dangerous trees will need pruning back, occasionally they may need to be removed entirely.
