What if towards the end of the day I find myself hungry, with 600 calories to work with. I have a lot of room for protein fiber, and carbs, but only a little for salt, sugar and fat. Now, just have to search the fridge, pantry, online recipes, etc for something that works...
The longer that takes the more likely you are to break down and just eat whatever is convenient.
Wouldn't it be nice if I could just click a button and have a list of recipes that fit into my current allowances? Or, what if I could set target macros per meal/day and get recipe ideas that fit them well, to simplify/optimize meal planning? That would be pretty neat, IMO.
You have everything that's needed to accomplish this. The data just needs to be married.