I worked as an apprentice in a shop for about 5 years, but in an informal way, and there was no "certification" involved. Whether I got, or kept, a job was all about whether I could do the work, or not.
Regarding car work, I went to an NIASE(now just the ASE?) class for about 2 nights, until I realized that it was only about American cars, and I only worked on British cars, so I quit. However, there was an interesting little bit of irony when I worked in the little shop in Georgetown in Washington DC, and the President of the NIASE owned a Spitfire, and I was the only one that he would allow to work on it, and I was not NIASE certified. I got a bit of a chuckle about that. Still do today!
To me, it comes down to ability. Sadly, real ability is not easily found in dealer service bays today, but if you really look for it, you might find somebody.
I have done my own work forever, and you will never see me in any dealer's shop anywhere, for any reason, other than maybe ordering parts.