Plato,
No, it's racially motivated. The exodus began just after the riots in 1967. AKA 'the great white flight'.
Detroit for example was like any college town in America before the riots, people walking the streets shopping, etc. To this day Detroit has never recovered and probably never will. especially with (you guessed it) the evil ruling class pumping heavy drugs into the inner cities for the love of money, and YES the government is behind the epidemic. That's what the 'war on drugs' is all about. The same creeps taking control of the drug industry (at least)nation wide.
*(evidence supplied upon request)
Some of the seeming need for increased services is an illusion. With more people per square mile naturally you would need more services. If the urban has 5 times the population then a 500% increase in services does not equal more. As for a wider range of services needed, I do not believe this is true either, only that people will travel to urban areas for those services because with the lower density those services are less profitable in those kinds of areas so they aren't placed there.
Rural probably has the greater need use per person. In rural eastern Kentucky there are dozens of counties, each with it's own school system, each with it's own fire service, police etc. Because of the way the counties are drawn and the very low population density they are using far more services, person for person, than people living in Louisville Kentucky. It's like this: the city has 25 schools, The rural countryside has 25 school systems.