Why do Lewis structures not always show the actual three-dimensional shape of a molecule?

Lewis structures do not always show the actual three-dimensional shape of a molecule because they are designed as a topological portrayal of bonding rather than a geometric one.12

While a Lewis structure effectively identifies which atoms are neighbors and how they are connected via bonding and lone electron pairs, it does not account for the spatial orientation of these bonds. The theory was developed to represent the octet rule and the distribution of valence electrons, but it does not provide information regarding bond angles or the specific 3D arrangement of atoms in space.123

To determine molecular geometry, chemists often use the valence-shell electron-pair repulsion (VSEPR) theory, which builds upon the foundation of Gilbert N. Lewis’s work. VSEPR theory posits that electron pairs repel one another, and molecules adopt shapes that minimize these repulsions, thereby predicting the directional nature of covalent bonds that Lewis structures alone do not capture.13