Here's why:

* Composition: Erasers are typically made from rubber or plastic, which are both good insulators. Insulators resist the flow of electricity.

* Functionality: Erasers are designed to remove pencil marks from paper without conducting electricity. If they were conductors, they could cause a short circuit or shock when used near electrical components.

However, there are some exceptions:

* Conductive erasers: Some erasers are specifically designed to be conductive for specific applications, such as electronic circuits or anti-static devices. These erasers are made from materials like carbon or graphite, which are good conductors.

* Erasers with metal components: Some erasers may have metal components, such as a metal clip or a metal eraser head. These components could be considered conductors.

In general, it's safe to assume that a regular eraser is an insulator. However, it's always important to be aware of the specific materials and components of an eraser before using it near any electrical equipment.