Theres a variety of maintenance issues. If its a older ship you have to contend with failing mechanicals. bilge pump motors quitting. Obsolete electrical components. Simply plugging the ship into the local electrical grid may not be practical. If you are going to get two decades of useful life from this hulk it will need a complete refit of its combat and housekeeping systems. The steering and propulsion systems could be discarded, but most of the ship would need a overhaul.
And of course some idiot would come along bothering people with his plan to refloat 'The Grand Old Lady'.
And of course some idiot would come along bothering people with his plan to refloat 'The Grand Old Lady'.