Here's why:

* Plant cells have cell walls made primarily of cellulose, which provides structural support and protection.

* Animal cells do not have cell walls. Their structural support comes from internal components like the cytoskeleton.

* Bacteria also have cell walls, but their composition is different. Bacterial cell walls are made of peptidoglycan, a complex molecule that gives the cell its shape and protects it from osmotic pressure.

So, while both plant and bacterial cells have walls, they are made of different materials and serve slightly different purposes.