Shearing shrubs and hedges can be appropriate in some settings- and with certain plants, but it shouldn't be the only kind of pruning you consider.
Shearing promotes density & a "witches broom" appearance on the outer edge of a shrub while entirely ignoring the inner structure of the plant.
We often see ornamental trees like flowering crabs planted near the entrance of a home. They are left unpruned for several years until it becomes obvious that they will outgrow the space. So they are sheared into balls. The idea of shaping a plant is fine, but the problem is that when shearing, interior branches are not considered at all. Major branches continue to grow and over time begin crossing and rubbing on each other in any breeze - this creates open wounds that can't heal. Because the exterior of the trees are so dense there is no air flow and fungal diseases can flourish.
We strive to site plants where they will thrive and fit the space with minimal pruning. That said, we think it's important to address structural concerns within the plant every few years to ensure it can live a healthy life and grow successfully.
UW-Extension has some good info on pruning available at https://hort.uwex.edu . Take a look and feel free to let us know if you have any questions.