Here's why:

* Viruses are not considered living organisms. They lack the key characteristics of life, such as the ability to reproduce independently, metabolize, or maintain homeostasis.

* Viruses are much simpler than cells. They consist of a protein coat (capsid) surrounding a genetic core of either DNA or RNA. They don't have the complex internal structures found in cells, like organelles or cytoplasm.

* Viruses rely on host cells to replicate. They cannot reproduce on their own. Instead, they invade cells and hijack the host's cellular machinery to create more virus particles.

So, while viruses are sometimes referred to as "particles," they are not cells. They are distinct entities that exist on the border between the living and non-living.