There are many, many reasons to raise FPAs. There are health benefits, food safety and security benefits, and environmental benefits. However, it's often the economic benefits that hit closest to home right now.
The economic argument was articulated wonderfully by Ed Phillipsen, a former Greeley City Councilperson. My favorite part is where he points out the economic insensitivity of the "why don't you just move to the city?" argument, by saying:
...this ordinance was doomed when Mayor Norton publicly questioned why people who want to grow eggs don't just “move to the country.” A solution only possible for the affluent and not unlike the comment of Marie Antoinette who remarked, when informed that the people had no bread to eat, “Well then, let them eat cake.”