Hello from the Bay Area of California!
The starch is to stiffen the material making it easier to cut straight and to match your edges to make it easier to do that scant 1/4" seam that is traditional in quilting.
There are no quilt police here, so do as you like! Some folks just don't wash their material, using the sizing put in at the factory to replace the need for starch.
This is a fun group, so glad you decided to hop on board!