Chickens within city limits!

The City of Camden has a law against chickens within city limits, the City of Nashville (a HUGE city) allows them. Why is it the cities place to tell me what I can raise on my property? If I am in no way desturbing any neighbors, traffic, or harming any one why can't I have chickens to have fresh eggs? Thier waste would fertilize my tomatoe plants, a win win situation for me. I of course plan on having a decorative structure and fence for the chickens, so as not to hurt my property value, so why not?