Because the number of measurements you'd care about is way too high, and even if you knew the size, that doesn't mean you know if the 'fit' is good for that kin

Because the number of measurements you'd care about is way too high, and even if you knew the size, that doesn't mean you know if the 'fit' is good for that kind of garment. For instance, this weekend I bought two pairs of jeans. That means I tried on about 20 pairs. Waist size was the least of the issues. Does if fit the legs? Does it fits my butt? Does my package fit comfortably? It's hard to make it all work at once.