The front-end alignment may be needed because ball joints, idler arms, and tie rods will all wear with use. This wear can eventually lead to one or both of the front axles being out of alignment when your vehicle travels down the road.
When the vehicle is driven in normal conditions, the tires should wear evenly across the entire tread. Tires that are too low on air pressure will wear out on the edges. This typically happens on both outer edges at the same time. Tires that have too much air pressure will be worn in the center of the tread. If the tire is out of alignment, it will wear out more on one side than the other.
If the vehicle always pulls to the same side at the same rate, it is typically not the road. The vehicle may be pulling because one of the front tires might have significantly lower air pressure than the other one does. Usually you can see that the tire is under inflated by simply looking at them. Make sure all the tires are inflated to the amount recommended by the vehicle owner’s manual. If the tires have the correct air pressure but you still notice pulling, bring your vehicle in for an alignment. This can get you back to having a comfortable ride again.