Luckily i only have to cook for myself, and my daughter when she's over. I never waste any food ever, if im extra hungry i'll cook a little extra, if im not quite looking for a big/main meal i wont cook as much. My daughter is a good eater, not really fussy, i wont give her what i know she simply wont eat, like Mushrooms for example
She eats most Veg though without too much fuss.
So no, i never waste food. I can understand it must be frustrating for bigger families with kids who can be so unpredictable at dinner time though, there's usually some leftovers, and not all leftovers can be kept.