In 3d Graphics polygon modeling is used because it is best approach to do the 3d graphics. It is well suited for Scanline rendering (which is algorithm that will do row by row basis instead of pixel by pixel or polygon by polygon)
The main advantage of using Polygon modeling is faster compared to other modeling.
Many of the 3d Graphics software like Maya, 3D studio max, AutoCAD and many more are using different format for Polygon modeling
Learn more about the polygon modeling in the below link