I would agree, if your lender does not give you a benefit to document, and you are not leaving the country, just register it with the state and put the numbers on the hull.
My lender required documentation, and charged about $500 which is absurd, but I let them do it because I did not want to deal with it. I am also in Michigan and decided to register as well. I find that the local sheriffs, DNR, and Coasties will want to check you out if they do not see state registration numbers. It is unusual here not to show registration so they check closer. Not a big issue, unless they find some other violation while checking documentation, just an inconvenience.