Why do some municipalities have residency requirements?

It's fine for a city of 1,526,006 people like the City of Philadelphia to require some top city officials to live within the City limits. It's goofy for a tiny city with a population of 13,000 and maybe recently losing homeowners because of crime to require it's top officials, especially police  to live within the city limits. Philadelphia Police are no longer required to live in the city:

Posted: Wed, Jun. 6, 2012, 3:00 AM

Philadelphia police officers staying put in the city

Monica Yant Kinney, Inquirer Columnist

 "Background
It is helpful to know something about the history of residency requirements to better understand the arguments for and against them. As with many other remaining vestiges of bygone days, there is a reason why many cities created them and in some cases still have residency ordinances. There is no clearly defined beginning of residency requirements.12, 13 The most commonly accepted origin of residency requirements in the United States seems to be that they derived from the spoils system prevalent in large American cities during the mid-1800s. In cities such as Chicago and Boston, the local ward bosses hired public employees, particularly police officers and firefighters. This practice ensured the ward bosses’ continued reelection by employees whose jobs were directly tied to the ward bosses. But it also provided a service to assist the ward bosses in collecting bribes and protection money."

From:
Residency Requirements For First Responders - The Pennsylvania ...

www.house.state.pa.us/CJPS/documents/15/v15_a6.pdf

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