Here's why:

* Porous: Cell walls are made of cellulose (and other polysaccharides in some organisms), which forms a rigid, yet porous structure. This allows water and other small molecules to pass through easily.

* Strong support: The cell wall provides structural support and protection for the cell, giving it its shape and helping it withstand internal pressure.

* Protects cells: It acts as a barrier against pathogens and physical damage.

While the cell membrane is also porous, it's not as strong as the cell wall. The cell membrane is primarily responsible for regulating the movement of substances into and out of the cell, while the cell wall provides the structural support and protection.

Let me know if you have any other questions!