That would be worth finding out with a bit more precision. Obviously, there must be an incentive to simply abandon the boat rather than dispose of it in a responsible manner. The only thing I could think of is that either it's the hassle of doing it or the cost of doing it that would cause somebody to just simply beach the boat or leave it tied up at a dock somewhere.
You were mentioning the release of vehicles from a marine service centre. Who has the authority to release a vessel to you for your disposal?