A number of foods have only metric measurements. It would be good to have the choice of deciding in English or Metric terms how much was consumed. Computers convert easier than humans. :-)

+1

I suspect many of the food you notice this were user entered and it depends on what info was on the label. In Europe it seems standard to quote the values per.100g.

In the case of weight measures I agree though - the number of grams to the ounce does not vary so if the info per 100g is known the info per ounce could always be calculated. Things are a little more complicated because in English (American) measure people often use volume measures for dry ingredients whereas in metric people tend to use volume measures for liquids. An automatic conversion from metric weight measure to English volume measure is not possible without knowing the density of the food and in the case of dry ingredients one would also need to know how they pack. If you put peas into a cup there will be air gaps that mean you get less weight of peas in than if you mashed them first.