Here's why:

* Eukaryotic cells are complex cells that have membrane-bound organelles, including a nucleus. These include cells found in animals, plants, fungi, and protists.

* Prokaryotic cells, on the other hand, are simpler cells that lack a nucleus and other membrane-bound organelles. They include bacteria and archaea.

So, to summarize:

* Eukaryotic cells (like animal, plant, fungal, and protist cells) have a nucleus.

* Prokaryotic cells (like bacteria and archaea) do not have a nucleus.