Why do pre-construction and design specialists typically take an interdisciplinary approach to their work?

to maximize employability options
to draw on a varied creative tool set
to integrate well with other team members
to understand the methods of the construction team

The correct option is this: TO DRAW ON A VARIED CREATIVE TOOL SET.
An interdisciplinary approach refers to studies and training that use methods and insights from several established disciplines  or fields of study. For pre-construction and design specialists, they usually take interdisciplinary approach so that they can draw creative ideas from various sources.