If a mechanic cannot centre the steering wheel with the wheels, he shouldnt be let near a car.

It does baffle me as to how incompetent some people are. There are many areas for adjustment or repositioning where it can be rectified.

Although saying that, a few years back a friend had some "specialist" work done on his Sierra including compression struts up front. The idiot who installed a new rack at the same time left the car with 1 full turn to the left and over 1.25 full turns to the right the rack was so badly fitted.
Not to mention the loose bolts he left on the custom rear swing arms..

So there are dangerous mechanics out there at all levels, from one's who know they are idiots, to ones who think they are competent