For bonsai designed to appear to be trees in a normal landscape setting, the shallow pot produces in the brain the impression of a broad expanse of land. This helps create the illusion that the tree is not what it is, namely, just a potted plant. For cascade and semi-cascade bonsai, the impression is one of a mountainside.Sacrilege post of the week!
BUT ...other than conventional practice and cultivated esthetics, why do we want our trees in shallow pots when larger pots would be easier to keep watered and fed and less susceptible to temp changes.
Kick me now.