ASE Tech certification can be in one of many categories, or in all categories. there are 54 different tests that are covered by the ASE testing and 18 different classifications of certifications. Roughly over 270,000 people are certified. I let my certification lapse when I changed professions, but the knowledge never leaves you. About 1/3 of the people taking the test fail, so the tests are not too easy.
Since the ase certification is not required to work at a dealership or even an independent shop, there are plenty of qualified and talented individuals that repair cars without being certified. Although it is a good idea and shows heir dedication to being the best they can by passing the certification.