Well, yeah, it's the very physical foundation bonsai is built on. I mean compared to a "real tree" you're working with less tree, less visual space, less soil, less, less less.
The ultimate visual illusion you're trying to create has vastly less detail and feature than what you're trying to picture. For instance, a bonsai has at most a few hundred, or thousand, leaves. A full-sized tree can have tens of millions...
Artistically, the less-is-more approach is more subtle. In Asian art, blank space is as valuable, or more valuable than occupied space. The tension is more natural for the viewer, I think, because the eye can be overwhelmed by too much detail (branches, leaves)...
This is a complex topic that cuts many ways in bonsai. I posted a link below a while back on esthetics in Asian art that addressed some of this in detail. Mono-no-aware, sabi-sabi and a few other Japanese ideals are tied up in this. Understanding those concepts can explain a lot of the artistic ideas in bonsai
http://plato.stanford.edu/entries/ja...-aesthetics/#2