To piggyback on this excellent post for anyone interested, AC and DC both have their strengths and weaknesses, so it's a right tool for the job situation.

Simplified, DC is better for small applications, AC is better over distance. Your computer is all DC on the inside. The power line to your house and most of the wiring in it is AC. That's why your electronics need an AC adapter, the big body plug, instead of just a regular plug. It converts AC to DC.