Here's why:

* Tissues are groups of similar cells that work together to perform a specific function.

* Specialized cells have unique structures and functions that allow them to perform their specific roles within the tissue.

For example:

* Muscle tissue is made up of muscle cells that are specialized for contraction.

* Nervous tissue is made up of nerve cells that are specialized for transmitting signals.

* Epithelial tissue is made up of cells that form protective layers and linings.

So, while all cells share some basic characteristics, the cells that form tissues have evolved to be specialized for a particular function.