It really comes down to what the occupation is.
Not all credentials are equal when it comes to quality of job performance skills and know how.
It's not uncommon for example for groups to create a set of standards or criteria simply for the purpose of keeping numbers of people down who want to pursue the profession and in other instances it may be a meaningless badge of honor that convinces the unknowing public that it means more than it actually does.
Not long ago someone posted a question regarding wedding photographers. They wanted to know if it would cause people to hire them if they had the credential Certified Professional Photographer.
In my opinion a photographer's portfolio, reputation, and references eclipses any designation they may have on their business card.
Another example is the CISP designation for inside sales reps which stands for "Certified Inside Sales Professional". In order for such designations to carry weight they have to be well known to the public and respected industry wide.
Right now there are things like Disc Jockey and Standup Comedy schools that offer certifications. They may give the students more confidence knowing they "went to school" for it but the professionals laugh at them for wasting their money.
Anything that involves medical, legal, and financial should definitely have standards and credentials along with anything that effects safety standards such as building codes, automobiles, and the like.
Having said that if my neighbor has 20 years experience tuning up cars I would not be oppose to having him/her look at my car. How many of us actually check out a mechanic's credentials?
Anyone can print out a form and put it in a frame!
If someone wants to braid hair I don't think they need to prove they have a certificate to braid hair. It's a form of protectionism for the most part. They don't want anyone to be able to hang a shingle in their window. What's next certified fast food worker?