“A couple of months ago, two Jehovah's witnesses came by while I was working on a tree. We spent about ten minutes talking about bonsai, not religion, before they went on their way.”
Nice -- turning of the tables, but I think that you could have kept them listening for another ten minutes.
All joking aside, I don't think it selfish one bit not to share an artform. Sometimes it is nice to keep something personal private. I create art as a graphic designer that is meant for public consumption and is seen by thousands (if not more) of people at stores and in magazines and even on TV commercials. I also create art that is more personal. It may be on canvas, digitally in the form of visual or audio, or the harmonious manipulation between order and chaos in nature (bonsai) that is shared with a select few. I find nothing wrong with this.
With that said, my bonsai are in their very beginnings, and to show them may open me up to critique. That is how we learn though. I use the word WE because WE all benefit (from even the worst looking tree) not only as "artists" learning the craft and the theories of bonsai, but also as teachers that may pass on the tradition of Bonsai to others. I feel that some may deem it neccessary to have a judged competition because it seems that that is a form of validation that makes anything we do in life serious and worthwhile.