Those locations have a large grid connection, which is valuable enough to pay for the decomissioning / cleanup costs so something else can use the connection.
Heck, there are companies cleaning up coal plants to use the connection for solar or wind, and that's a lot more expensive than cleaning up an old solar plant.
Heck, there are companies cleaning up coal plants to use the connection for solar or wind, and that's a lot more expensive than cleaning up an old solar plant.