I've had problems with several major alignment places over the years. Laser aligned with computer printouts which are very impressive and show the alignment to be spot-on but afterwards the tyres wear unevenly and steering wheel is not straight. I think the measuring equipment is probably fine but the jigs they bolt onto the wheels may have been dropped or thrown around by the apprentice when nobody was looking and could often be way out of calibration.
After several visits to the last laser/computer aided alignment centre I decided to do it myself with fine threads, two long sticks and a lot of time measuring the setup with a ruler (there's how-to guides on the web). It confirmed one wheel was pointing out too far by about 6mm, and after adjusting and checking still using the string and stick method I then found the steering to be centred and tyre wear has been perfect for over four years now. Once you've spent time fannying about with stick and string it's easy and I'd never go back to a major alignment centre and risk bad alignment.
I have a local tyre dealer who is a stickler for getting things right and he swears by his mechanical alignment jigs, and doesn't trust the laser jigs. Great when they're new & calibrated but not so much when they're mistreated and unchecked.