Here's why:

* Components: The internal components of a computer, like the CPU, RAM, and hard drive, are designed to operate on low-voltage DC power.

* Efficiency: DC power is more efficient for electronic circuits than AC power.

* Safety: DC power is generally safer to use than AC power, especially at the low voltages used in computers.

However, here's the catch:

* Power Supply: The computer's power supply converts the AC power from the wall outlet into DC power that the internal components can use. This process is crucial for safe and efficient operation.

In summary: While a computer runs on DC power, it still needs an AC power source to function. The power supply serves as the bridge between the two, converting AC to DC.