...because you need a bonsai
Cultivation

Bonsai can be created from nearly any perennial woody-stemmed tree or shrub species which produces true branches and remains small through pot confinement with crown and root pruning. Some species are popular as bonsai material because they have characteristics, such as small leaves or needles, that make them appropriate for the compact visual scope of bonsai. The purposes of bonsai are primarily contemplation (for the viewer) and the pleasant exercise of effort and ingenuity (for the grower). By contrast with other plant-related practices, bonsai is not intended for production of food, for medicine, or for creating yard-sized or park-sized landscapes. As a result, the scope of bonsai practice is narrow and focused on long-term cultivation and shaping of one or more small trees in a single container.