You don't remove theming elements from a themed area just because you've decided to close the ride. You remove the ride name signs and thrill guides and such, because the ride isn't "there" but all the themed elements can stand on their own as themed elements. Why spend money to remove them? why task employees to the work when there is other work to do?
Why didn't Dreamworld demolish the tower of terror station \ tunnel \ tower-track? Because you don't, unless you need to (or unless you already have a crane on site for other purposes and you can make the most of its down-time).
If the area can still be accessed and used by guests, maintaining the theme is, for now, desirable.