Here's why:

* Structure: Carbonic acid exists as a molecule with a central carbon atom bonded to two oxygen atoms and two hydrogen atoms. The oxygen atoms are also bonded to each other.

* Bonding: The bonds between the atoms in carbonic acid are covalent, meaning they involve the sharing of electrons between atoms.

* No Ions: In a molecular compound, the atoms are held together by covalent bonds and there are no distinct, charged ions present.

Important Note: While anhydrous carbonic acid is a molecule, it is very unstable and quickly decomposes into carbon dioxide (CO₂) and water (H₂O).