I used to live in MD, where I didn't need titles, registration, or insurance for my scooters. I always wanted to take one with me when vacationing at the Jersey shore, but knew about NJ's strict laws, so I never did.
Frankly, it's a states rights issue, what vehicles they allow on their roads, and it's up to us to make sure we're legal.
Case in point: I since moved to NJ and now can't ride my scooters at all. Since I didn't need titles in MD, I never got any, and in NJ anything without pedals is a motorcycle, which requires full paperwork. I don't have any right to keep using them here, even though they were legit in another state.
You really have to keep on top of local laws, so do some research before planning a ride. In Princeton Township, there are no local ordinances regarding mopeds at all, whereas in Princeton Borough, just a mile or two in length, you can't park mopeds on sidewalks except at bicycle racks. Local cops are paid to enforce their own local laws, and won't take ignorance lightly.