In Michigan you can't just go out and "cruise" on an antique plate, you can be ticketed by law enforcement, believe me I checked as it would save a nice chunk of change on my insurance. The reason it is a big savings is because you can only use your car for events, parades etc.
With that said I don't know how many, if any, people that have been ticketed for doing so. When you contact the SOS and Hagerty they both tell you the same thing.