Question

Why is the cell theory a theory and not a law?

Answer 1

from wiki:

The cell theory states:
1. All living things are made of one or more cells
2. Cells only come from preexisting cells
3. Cells are the smallest unit of life
And there are more things now that we use to consider it to be "living". The activity of an organism depends on the total activity of the organism's cells, and all organisms have some kind of energy flow or metabolism.

The first reason that the cell theory is a theory is that viruses are a big exception to it. Viruses are not made of cells, and they don't have a metabolism and the activity of an organism depends on chemical reactions, but some scientists still consider them to be alive, so that goes against what the cell theory says.
The second reason is simple...the first cell in the world obviously did not come from a preexisting cell.