Microstructural modeling is often viewed as an extraneous activity when analyzing the behavior of composites. Many engineers use the "system" properties as the inputs for their part design without considering what contributes to that overall system response.
Many companies that develop new composite materials are surprised when their product does not perform as expected during the physical testing and certification process. In addition to the many years wasted on developing the material, companies often spend more than $50M on developing and testing a single new material concept.
Have you ever experienced your car breaking down due to part failure, with little or no warning? This could be because the part was designed without taking into account how it would be affected by material behavior or manufacturing variability.