Hi - apparently they are snap frozen and could retain the vitamins better than veggies that have been transported or lying around the store for a week. Even if that is not true, better to supplement your meals with frozen veg than be tempted to add a grain. I keep them handy for that reason.
It IS very difficult if you live alone to have a variety of veg and eat them before they go off. I wonder if that is why I use to not bother and have cheese on toast instead :-)