Edges in 3D models are often hidden because rendering workflows prioritize surface materials (textures, shaders) over edge definition to achieve realistic or clean visuals.
This focus helps models look seamless—critical for applications like film, games, or product design—where visible edges might break immersion. Most tools default to this approach to mimic real-world objects, which don’t have "outlined" edges.
If you need to see edges (e.g., for modeling tutorials or technical checks), use wireframe view or enable edge outlines in your 3D software settings—no need to modify the model itself.