Here's why:

* Cells provide energy: Cells (or batteries) are the energy source for many circuits. They create an electrical potential difference (voltage) that drives the flow of electrons.

* Other energy sources exist: There are other ways to create an electrical potential difference. These include:

* Generators: Convert mechanical energy into electrical energy.

* Solar panels: Convert light energy into electrical energy.

* Thermoelectric generators: Convert heat energy into electrical energy.

* Electromagnetic induction: Changing magnetic fields can induce electric currents.

Examples of circuits without cells:

* AC power circuits: These use generators as the energy source.

* Solar-powered circuits: These use solar panels to generate electricity.

* Induction cooktops: These use electromagnetic induction to heat cookware.

In summary: While cells are a common energy source in circuits, they are not the only option. Many circuits operate without cells, relying on other energy sources to create an electrical potential difference.