These structures got old and weren't replaced. This is plain old urban decay.

Some places let their old stuff decay and get vandalized. Others tear down their old stuff and don't replace it.

But some cities - not all - tear down their ugly old stuff then - gasp - rebuild something else there. If they make that a habit, it's just expected. In such cities you look around and everything is either too beautiful to tear down, or too new to be run down.

Come to Sydney some time, it's beautiful :)