Reality is that it is a bit of both. Certification is really needed only in professions where safety or large amounts of money or public interest is an issue. Otherwise, it is just a union by a different name, whose members try to exclude others from competing in their line of work. Having said that, it does give clubs and customers a little more confidence in a guy, even if it only is for the most basic safety reasons, like allowing him to work with a girl. It give a feeling of traceability and accountability.
In this very forum, you will find ordinary rec players providing superior tips and insights into the game compared to several coaches.