Left to their own devices, some would probably donate the cheapest food imaginable...tinned meatballs, or macaroni...or even out of date food. Sorry if I sound cynical. But depending on the food bank users level of need, a treat, or something that appears 'unnecessary' may make a difference to enjoying what they've recieved or creating a bit of variety in meals. Maybe that bag of sugar will allow a needy parent to bake.
Giving the needy things that are not 'needed' does not mean things are better than what's been reported regarding UC and the growing numbers of those in need.
We could also just give them bread and water I suppose.