In the years after World War II, tomato soup served with grilled cheese sandwiches became a popular school cafeteria menu combination that carried over into home kitchens everywhere. Here's the most plausible explanation I've found for why this happened: institutional food service (including school cafeterias) paired grilled cheese with tomato soup to meet the minimum school lunch requirements for sufficient Vitamin C (from the tomatoes) and protein (from the cheese). As canned soups became more available and economical, and processed cheese extended its shelf life, soup and sandwiches were a practical choice for many school systems. Today there's only one reason we eat grilled cheese and tomato soup -- because it's still the best comfort food combination around. Of course, you can fancy up the cheese and bread in your sandwich, but at the end of the day, nothing beats a basic creamy tomato soup. When it's this easy to make soup from scratch, there's no reason to default to canned soup. By the way, both of my grandsons are dunkers, just as my school friends and I used to be, and this soup makes for great dunking of melty grilled cheese sandwiches.