Here's why:

* Structure: Paper is made from cellulose fibers, which are primarily composed of carbon, hydrogen, and oxygen. These materials don't have free electrons that can easily carry an electric current.

* Resistance: Paper has a high electrical resistance, meaning it opposes the flow of electricity. This is because its electrons are tightly bound to the atoms, making it difficult for them to move freely.

* Moisture: While dry paper is a good insulator, moisture can significantly decrease its resistance. Wet paper can conduct electricity because water molecules can carry an electric current.

Exceptions:

* Special Paper: Some types of paper, like conductive paper, are designed to conduct electricity. They often contain materials like carbon or metal particles that allow for better electrical conductivity.

* High Voltage: Under extremely high voltage conditions, even paper can experience dielectric breakdown, allowing current to flow through it. This is why it's crucial to use proper insulation in high-voltage applications.

In summary: Paper is typically an insulator, but its conductivity can be affected by factors like moisture and the presence of conductive materials.