I know someone is going to shoot me down for this, but to hell with it.
I tend to watch the guys when they do my wheel alignment and when they go to tighten the bolts they have losened to align the wheels they don't put too much effort into tightening them back up. Just a single half turn on the bolt and that's it. No matter how many places I go, it's the same.
I find that a brand new car won't need a wheel alignment for a couple of years, then once you get it done, you need to redo it every 6 months (or less) . I suspect these half tightened bolts if done tighter would mean that the wheels wouldn't be knocked out of alignment so quickly.
OK that's my conspiracy theory out in the open now. Where's Michael Moore when you need him?