This, I would argue, is the point at which art and craft merge. Were the maker to take any less care in engineering the piece efficiently as a tool, the piece would be significantly diminished and would move from being the highest expression of its form to a mere object, a thing. If, for instance, a pipe did not have a draft hole, it would, in many ways, cease to be a "pipe." This is why, in any given medium, it is important to operate within certain parameters. With the bounds of the expression limited, the artist/craftsman must call upon increasingly greater skill and creativity in order to articulate something extraordinary. Necessity, as they say, is the mother of invention.
One needs only to think of Sixten's skillful use of bamboo during the war. Briar was not being exported from italy, there was a limited amount, and blocks were cut in half to stretch the supply. Since pipes need shanks--though one can point to exceptions for this--Sixten engineered a beautiful, elegant, and ultimately successful expression of "the pipe," using bamboo instead of briar for its shank. By moving outside the general principles of pipe aesthetics yet staying within the confines of what properly constitutes a pipe, Sixten elevated the expression of form within the medium, "pipe."
For those of us that hope our work will be judged to have done likewise, the boundaries of expression are not a static force, but a malleable set of principles whose governance we submit to willingly. In the end, the artist works collaboratively with such boundaries in order to elevate the craft.
For my own part, I care little if a pipe is smoked or simply admired as a functional object. Over the years, I have created multi-thousand-dollar pipes that I knew would never see a flame, and others that, to my delight are smoked on a very regular basis. To my mind, a pipe's "true purpose" is not necessarily fulfilled when it is smoked, but when it is enjoyed.