Here's why:

* Almost all prokaryotes have a cell wall. This rigid outer layer provides structural support and protection, helping the cell maintain its shape and withstand changes in osmotic pressure.

* Eukaryotes (like plants, fungi, and some protists) also have cell walls, but they are composed of different materials than those found in prokaryotes.

* While other features like flagella, pili, and capsules are common in prokaryotes, they are not as universally present as cell walls.

Let me know if you have any other questions!