Have you ever heard of Dry Steering? This means you are turning the steering wheel with the vehicle completely stationary. This can strain your power steering system (rack and pinion, pump, tie rods, bearings) and prematurely wear your tires. Being nice to your tires is highly recommended, since they’re the only things keeping you in contact with the pavement; not to mention cost and safety issues (you could be grinding rocks into your tread which could go flying at high speeds).
Avoiding dry steering is fairly easy with some practice. Simply make sure the vehicle is moving – if even at an incredibly slow speed – while you’re turning the wheel.