Most knitwear is not knitted to shape. It is knitted flat in large panels, cut with a blade, and sewn. It is faster, it wastes about a fifth of the yarn, and it puts a cut edge inside every seam.
Knitting to shape
Knitting to shape means the machine increases and decreases stitches to produce the finished panel, so nothing is ever cut. The Rib Vest has no cut edge anywhere in it and no seam across the shoulder.
It takes roughly three times as long per garment and the machine needs setting up for every size. That is most of the reason a fine-gauge vest costs what it does.
The rib does the fitting. That is the whole argument for knitting rather than cutting.
What it does for the wearer
A knitted trouser with a drawn waist and no closure takes the shape of whoever wears it. A cut trouser imposes one. Neither is better in general; for the thing you change into at the end of the day, the first is obviously right.
