Housing costs were the first reason for leaving. Then the lack of services, high taxation and the riots, accelerated the decline. Well, they certainly have eliminated "housing costs" as one of the reasons.
I can think of a few more:
1. Racism and racial politics
2. Unions
3. Total degeneration of the culture
Feel free to add your own additions.
There is trouble brewing within the UAW which could explode into an all out union on union war. Seems that members are getting a little tired of the union blowing big bucks trying to force people to unionize when they don't want a union.
Be sure to check out the video
UAW: War on the factory floor?