Floss can remove food particles that get stuck in between teeth. That food will promote bacteria that cause a rather foul odor, so it should be removed. I've been around many people that don't floss and the smell of their breath is noticeable and disgusting. At the very least, one should floss to help prevent that.
This is another case of profitable oversimplification. Do dogs brush their teeth and floss? Do most animals with perfect teeth do deep cleaning and stuff? We again built an industry around bad habits and poor (but affordable and profitable) diets!
Also posted earlier at <a href="https://news.ycombinator.com/item?id=12208402" rel="nofollow">https://news.ycombinator.com/item?id=12208402</a> though no discussion there (yet?).