The approach is very elegant. DNA is uniquely good at manufacturing molecules. Some of the proteins the nature can make are amazing. So if you want to assemble something on the molecular scale this is probably the way to go.
http://en.wikipedia.org/wiki/Ribosome
What you said is like saying "software is very good at welding auto parts", when in fact, it is industrial robots that can weld, but a paper printout of the control code would not be capable of welding!
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Although DNA cannot be used for biomanufacturing in the way you describe, if you want a different but still interesting example of DNA being used for mechanical purposes, you could look at DNA origami:
DNA origami takes advantage of DNA's ability to self-assemble fairly predictably into 3D shapes based on the designer specifying 1D sequences of letters, which bind to each other with certain propensities.