Here is a cartoon illustration of the steering system. The tie rod is in purple.
* it is mechanically connected to the steering wheel
* it controls the angle of the wheel relative to the center-line of the car (i.e. the "toe")
* it has a thread which allows its length to be changed
* left and right tie rod are independent (in length)
ideally, the steering wheel is centered before the wheel adjustments and alignments is started. you can appreciate it is not immediately easy to gauge that the steering wheel is slightly off, when the car is static. the steering wheel also bounces a bit when you make small adjustments while the car is still. so most techs probably just "eyeball" it , and hence the bad end result.
it is possible to have all the wheels fully aligned -- symmetric and etc so that the car tracks properly -- but the steering wheel itself is off-center. (you can imagine if the wheels are perfect, but the steerng wheel was removed rotated and reattached).
the solution isnt to disconnect the wheel from its hub and reattach it (angles are not very fine), but rather to simultaneously adjust both tie rods lengths to move the wheel in parallel , symmetric to the car, when the steering wheel is perfectly centered.
i cant trust techs to do a great job at this. so if things are not perfect after a shop alignment, id probably go back and tweak the tie rods myself until its perfect