Why can't an antibiotic help when you have common cold?

Common Cold is a virus as opposed to a bacteria. Antibiotic can only act on bacteria as the bacteria is living organism.

Virus is a packet of DNA or RNA embedded in a protein that masquerades itself and enters a living cell. It then takes over the entire metabolic process of the cell to destroy the cell it entered and uses it to create more protein packets like itself ready to attack other cells.