Yeah, line spacing helps you set the speed and response of the controls. Works in concert with the horn lengths on the flaps and elevators. You can even set the up or down individually if you have a model that turns faster one way or the other. Very handy to have a handle that will let you adjust it in this way. Everybody is different, and has different reaction times and comfort zones, so that is why you need to set it up for what feels good and comfortable for you.
And it is kind of like power steering in a way. And I don't think there are too many race cars on any kind of track that don't have power steering. Maybe top level drag racers don't, don't know for sure, but midgets, sprint cars, Indy cars, NASCAR stock cars, Formula One, just about everything has power steering. In the old days, I have read where drivers would swap around steering wheels of larger or smaller diameter to help there feel of the car, and I imagine todays drivers have that option also. It's all about leverage and feed back from the car to the driver, or from the model down the lines to the pilot.
Experiment a little on a nice day with a spare airplane if you don't want to use your nicest model, and you'll see what I mean.
Good luck and have fun,
Dan McEntee