Even without Agriculture, each farm is adding + 1 food and + 3 commerce per tile after Sanitation. This is far better than the town's + 5 (+ 6 commerce with taxation), considering a financial leader. The more happiness you get in each city makes it progressively more and more powerful, letting you work more tiles and add specialists. Below the happiness cap, cottaging is good, but as your cities grow larger the extra food really helps. While city states is a very powerful civic (too powerful in my opinion), I still believe that Aristocracy has its place for certain leaders and strategies.