rebdoniel, you’ve clearly never tried shopping for a frum woman! The BIGGEST issue is with necklines. Non-Jewish women wear long sleeved shirts, and shirts with high necklines, but “never the twain shall meet” (well, rarely the twain shall meet). It is so hard to find tznius shirts. The ones that do exist tend to be form-fitting, and if you try the next size up the sleeves and hem will be too long. (The same can be true of skirts). It is so annoying to have to wear a shell underneath everything, especially in the summer (and you can’t find shells outside of the frum world, and have to pay a premium). It is almost easier to wear a high-necked sleeveless shirt with a cardigan sweater, but I try not to do that in the hot season because of the temptation to remove the sweater.
The best places to find tznius clothing outside of the frum world are companies that market to older women, like Christopher & Banks and Newport News. It is hard to wear their clothing without instantly adding 15 years to your appearance.