Christie, this is my guess as to what's going on. I've been looking into dress sizes lately, and the measurements used for a size "small" dress are (although they seem to vary from company to company) something like this:
bust: 34"
waist: 26"
hips: 36"
I guess this means that an "ideal" figure which has a 26" waist also has 36" hips. Since the waistband of the jeans almost always fits somewhere way below your natural waist -- much closer to your hips, actually -- its waistband circumference is going to be much more than 26". Depending on how low the rise is, the waistband of a size 26 pair of jeans is probably in the vicinity of 32 or 33 inches. I just measured the waist circumference of one of my pairs of size 26 low-rise jeans, and it was about 33".
As it happens, the size of jeans that fits me is usually 25 or 26 (I even have a couple of pairs of size 24!) but my waist is nowhere near that small -- it measures 28" or 28.5", depending on whether I've just eaten or not! But my hips are slim -- only 34" -- and since my jean waistband fits around my hips, not my waist, it doesn't matter that I don't have a tiny waist. It seems that an "ideal" woman whose hips are 34" will also have a 24" or 25" waist. Ha. Guess I'm less than ideal.
Does that make sense?