Legislating Aesthetics

On a south Tampa street where Christmas block parties are a tradition, residents are arguing about whether their property should be earmarked a historic district by the city. ...At city hall, historic preservation staff members say maintaining the character and fabric of Tampa is an important endeavor. They also tout economic benefits for owners of historic buildings, including tax breaks and increased property values.

If designating the property as part of an historic district is so desirable, why are tax breaks necessary to encourage it?