Let's apply this theory to the fashion world, yes? The smaller the person, the bigger the margin of error.
Figure A.

See, a thin person has a larger margin of error as far as clothing goes. Your pants can be a little lower, your shirt a little higher. Heck, you could walk around in a bikini and no one would mind much.
Figure B.

A larger person has a smaller margin of error. Your pants need to be higher and your shirts need to be lower, thus preventing any sightings of belly or bottom. Because let's face it, I don't want to see Figure B. walking around in a bikini.
So, now that you have the rules, I don't want to see any more of this.....

Thank you. Fashion Tips courtesy of MomBabe.