Power
Aside from the director, you are the big boss man (or woman). The whole art department looks to you as their leader and you can hire or fire who you want.
Your skills and creativity give you the power to make a movie special—award-winning, even. Quality production design is always important, especially on period pieces and big budget splashes.
Some movies rely on their production design to draw people in and hook them. After all, big time space movies wouldn’t be so cool to watch on IMAX if they looked small, drab, and boring.
The movies that Baz Luhrmanm makes are meant to be musical feasts for the eyes. If you don’t do your job, your films will look more like microwaved leftovers.