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To illuminate reason number three above:

While no garment would require nine yards of fabric, a seamstress friend of mine tells me that in the glory days of tailoring it would sometimes be appropriate to use that much.

To make a suit of the most exceptional quality, one would want precisely align the grain of the fabric of each small component of the suit (i.e. the sleeves, the collar, etc.) This would require that vast amounts of fabric go wasted, so that in order to make a complete suit, one would need a total of nine yards of fabric.