Why are viruses not classified into any of the kingdoms?

Virus:

1. Viruses are microscopic organisms that are said to be the connecting link between the living and non-living entities.
2. They were not placed under the five-kingdom classification since they were neither considered living nor dead.
3. Hence, they are placed in a different group altogether.
4. Viruses lack cells and cell organelles, because of which they depend on the host cell's mechanism to reproduce and form proteins.
5. Viruses are even smaller than bacteria.

Therefore, Viruses are not classified into any of the kingdoms from the five kingdoms.