This subject will get mixed feelings from various hobbyist. There are factors to reflect on...With both Domestic and Wild Discus they need time when brought into a new environment. Location of tank if in high traffic area can spook them. Shadows that suddenly appear can spook them. With Wild Discus most often they feel comfort with driftwood furniture which closely relates to their prior environment.
I would say if you have domestic Discus it maybe more of a layout biotope preference for the hobbyist and not a need for the fish.
...Ralph