Don't you think that weight (or, pedantically, mass) generally makes more sense for many ingredients? 100g of flour is a well-defined quantity, one cup of flour can vary significantly depending on how tightly packed the flour is.
The packing is mostly a function of how you yourself put the flour into the cup/how it was handled and stored before I got to my house. In practice there's not much variation of this sort. And you still want to taste and adjust as needed, so I don't think you would really need to-the-gram precision since there are so many factors like humidity that can impact how much of an ingredient you should use anyways.
