I think it's about more than just wasted food... I think it's more likely that they love each other very much and she wants to send him off with a little something from home.
Food is a way of saying "I love you." Like, sure, you could stop and grab something along the way if you're peckish, but here, I took some time and prepped you some yummy goodness because I don't want you to get hungry.
7'