Here's why:

* Support and Structure: Cell walls provide structural support and rigidity to plant cells, allowing them to grow tall and maintain their shape.

* Protection: They also protect the cell from damage and bursting due to changes in osmotic pressure.

* Composition: Plant cell walls are primarily composed of cellulose, a complex carbohydrate, along with other polysaccharides like hemicellulose and pectin.

Animal cells, on the other hand, do not have cell walls. They have a cell membrane, which is a flexible structure that regulates the passage of molecules in and out of the cell.