Why are viruses called obligatory intercellular parasites?

Viruses:

1. Viruses are acellular organisms that consist of a capsid made up of protein and genetic material.
2. They lack the enzyme responsible for the synthesis of protein capsid.
3. Viruses use the machinery of the host cells to reproduce.
4. They do not have cell organelles such as Golgi complex, mitochondria, lysosomes, ribosomes etc. hence, they cannot reproduce or live separately.
5. Therefore they are called obligatory intercellular parasites.