Licensing and certification are and should be two different things. Licensing is a standard that the government requires to be met assuring that those practicing in a given profession are in fact meeting those standards. It protects the public from unscrupulous operators who will cause more harm than good. While the self taught individual may be as knowledgeable or better than a school educated person, it's harder for the consumer to assess that. Once trees are seen as critical parts of our community infrastructure then maybe there will be more effort toward licensing. In NJ there is a program in the making.
Certification on the other hand is a competitive advantage. For the public, it provides assurance of the person's credentials and that they are keeping their knowledge current to a prescribed level. We see this in a variety of professions. Think of accountants, there are different bodies they can join and become certified by. CPA, CA, CGA, CMA, which one suits you is entirely up to you but first you'll be able to ascertain the least of their knowledge by the credential they carry.
So, what's behind that patch and sticker is a third party that consumers can turn to.