Here's why:

* Copper is a transition metal: Transition metals generally don't readily react with strong bases like NaOH.

* Oxidation: While some metals react with NaOH, this usually involves oxidation of the metal. Copper, however, is relatively resistant to oxidation in alkaline solutions.

* Passivation: In the presence of oxygen, copper can form a thin oxide layer on its surface. This layer acts as a protective barrier, further preventing reactions with NaOH.

However, there are a few caveats:

* High temperatures and concentrated solutions: At extremely high temperatures and in highly concentrated NaOH solutions, a very slow reaction might occur.

* Presence of other oxidizers: If a strong oxidizer like hydrogen peroxide is present along with NaOH, copper may react to form copper(II) hydroxide.

In summary, under normal conditions, copper is not soluble in sodium hydroxide.