These quads were never meant to be driven on the roads!! The tires are for OFF road and don't have the traction that a street tire does. It's easy to spin out and lose control. I was a rider of ALL motorcycles in the past. NOW??? No chance you would get me on a bike on the island or at home! People are way too distracted to pay attention . Let alone have respect for bikes. The government needs to address this with the rental companies!
I haven't owned a car in years, but drive a motorcycle all the time in all conditions. One needs to be much more careful on a bike than in a car.
I think that there's no need for rental companies to additionally "police" their clients. If someone old enough and with a valid driver's license wants to rent something, then they should be able to do so. The other side of that is the high rate of accidents on scooters and mopeds from rentals in areas like Greece, Thailand; in the latter case the lack of medical care is big thing. The government could reclassify vehicles that are current street legal as no longer being so; but I'd be more than a bit surprised if that happened.