Because your Power Steering pump is robbing power/ RPM'S from your engine. This is common in all vehicles with power steering.
It is time for a professional car mechanic to have a look. The steering may be caused by dry joints (needs greasing), the revs may need the engine to be adjusted to run slower.
Horn ring and/or steering wheel hub is bent.
put the key in the ignition and turn the steering wheel and the key at the say time (turn the steering wheel to the left)
Turn the steering wheel right to turn right in reverse.
2003 ford expodition steering wheel is hard to turn.
Put the key in and move the steering wheel until the key can turn
Try pulling on the steering wheel one way or the other while you turn the key.
The power steering fluid is thicker when cold therefore it is harder to turn the wheel.
Power steering fluid helps your steering wheel turn easily. If you have dirty power steering fluid, it may be hard to turn your steering wheel while driving.
Check the fluid in the power steering. If it is low the car will make noise when you turn the wheel.
look back and when you turn your steering wheel left it goes right so turn the steering wheel the opposite way
Jiggle the steering wheel as you turn the key. I've owned several cars in which the steering wheel lock wouldn't let the key turn if there was any pressure on the steering wheel lock.