Ah, seems you're right, turns out in the UK most garages do MOTs. Where I come from, that would mean every car could be passed without being roadworthy, as no garage would voluntarily declare a car they've been maintaining as unroadworthy, plus you could just throw your mate a 50 euro note. So instead, we have certifications and licenses for TÜV inspectors and they get taken away if you get caught. There have to be cameras for investigators to see what was checked on any particular car and what was not. They can catch you if you pass a car with something like a malfunctioning light bulb. There's spot checks (rare tbh) and of course if a particular garage or inspector is being suspected, they'll be under extra surveillance. Plus you need equipment like the suspension and brake testers, so it doesn't make sense for every single garage to join the org (paid membership), invest thousands if not tens of thousands in equipment plus all the mechanics to get tested, as there just wouldn't be enough demand.