Here's why:

* Location: DNA is primarily found within the nucleus of a cell, protected by a nuclear membrane.

* Function: DNA carries the genetic code for an organism, and it's crucial that it remains stable and protected. The cell membrane's primary function is to control the movement of substances in and out of the cell.

While DNA is not found in the cell membrane, there are some exceptions:

* Mitochondria and chloroplasts: These organelles have their own DNA, which is located within their respective membranes.

* Bacterial DNA: In bacteria, DNA is located in a region called the nucleoid, which is not enclosed by a membrane but is associated with the cell membrane.

Let me know if you have any other questions!