If you asked a hundred people, you’d find that most have never even heard of having their power steering serviced. Since most cars have hydraulic power steering assist, they have a pump to pressurize the fluid, and like all such fluids, it gets contaminated. That contamination can be debris from wear or water from air seeping in and condensation.
Water is corrosive and damages expensive power steering components. Removing the old fluid, and flushing out the system, gets rid of deposits and water. Clean, fresh fluid lubricates and provides better corrosion protection.
Ask Ace Auto Doctor & Repair, or check your owner’s manual, to see when power steering service is recommended. It’ll extend the life of your power steering components, from pumps and hoses to expensive steering racks.