It comes down to the fact that the ingredients we buy from the stores near us tend to come in nice round numbers in our local measuring system, and recipes tend to be tailored to that. For example, "1 cup of shredded cheese and 1lb sausage" may translate precisely to "236.9 mL shredded cheese and 0.45kg sausage", but your nearby store selling metric ingredients may have shredded cheese in a 300mL bag and sausage in 0.5kg packages. So you either measure very precisely and waste food (which makes the recipe a pain to get right), or try to use the local equivalent (and the recipe might not end up tasting the same as a result.) So there ends up being some "art" to doing a proper translation.
For baking, precision is important, but subsequently most recipes are precisely specified, so the conversion should be followed pretty exactly. For most non-baking recipes, precisions is much less important, so a 'recipe translator' could either perform some rounding (maybe there should be a 'level of precision' metadata element for recipes), or, I could just do the rounding in my head and use my critical thinking facilities rather than following the recipe blindly.
