resident means.. if your are permanent resident with verified address. If you are working in MI and paying Tax to state of Mi than you are MI resident. if I go there for few days I can drive with my NY license . But if I am staying there for ever and moved there than I have to go to DMV, fill application and do eye test and get converted my NY license to MI license.
its required for law enforcement. as any points and violation record will go on your license. if you are MI resident you should have MI license so that you can be tracked.
Every state require their residents to have the license of the state. Also the car registration should be of same state in which you reside.