Derelict ships on Lake Union

A curiosity I was unable to find a decent explanation for online… visited some live-aboard friends and was looking at “Highland Light” on Lake Union. It is the primary example of my curiosity, as it is a 244ft stern trawler that has been in the same moorage since 2010. Its in horrible condition. Moorage on Lake Union is in high demand. Who the hell is paying monthly(?) for that, and many other vessels to deteriorate, unused in such a location? The area by the locks seems to be loaded with large and small boats / ships which have not seen use in years. Do people have grandfathered slip rates or something? Its just really baffling how many unused vessels are presumably paying for spots. My curiosity is mostly targeted at A: large derelicts which i am guessing have wild moorage fees, and worthless smaller vessels who are paying the value of their boat in slip fees every month.