There are countless reasons why soup is such a great option for cooking right now. The most obvious factor is that we generally like to eat foods opposite in temperature of the weather outside. So, on cool fall days like these we like something to warm us up. Just like how on those scorching hot days of summer we were eating low temp foods like salads. Though perhaps less obvious to some, is the availability and quality of the local produce in relation to soup. Although the warm days are more or less behind us for now, we can still find some produce like tomatoes, peppers and corn hanging around until full frost arrives. Though the supplies grow increasingly limited and quality tends to decrease, this is exactly why they are ideal for the soup pot. Perfect quality is not really necessary and mixing things up with what's available makes sense when considering the versatile nature of soup. The opposite is true as well - when you have so much of an item and don't know what to do with it, you can probably make it into soup. For instance, when corn is inexpensive and thriving in August, I make a few pots of corn chowder.
Not to mention, take into account everything that is in its prime now - winter squashes, root and onion crops, for instance - and you can probably cook up soup once or twice a week now through the winter and never run out of new ideas. When you do so, make it worthwhile by cooking a large pot that you can get multiple meals out of. Or, why not prepare two soups with similar bases at once? Keep in mind that since soup is liquid based, most freeze well without much change in quality. You'll never have to rely on canned soup again!