As the whole universe can't be observed , a scientist who studies a model which is an adaption of a widely accepted theory about the universe, the scientist would be able to understand the facts related to universe which can't be observed easily.
For example- the most accepted theory about the universe is the Big-Bang theory which states that the universe is continuously expanding and its temperature is decreasing. We cannot experience or observe the expanding procedure physically, so a model explaining this concept would help the scientist in understanding these facts more easily.