The field of dog training is an unregulated one. A fact that, unfortunately, is not common knowledge.
Anyone can deem themselves a dog trainer if they feel the urge, no experience, or even an affinity for dogs, necessary. Many different occupations are required to be licensed or certified by the state to practice said business. This licensing is unique to the field of which it governs and requires its possessor to pass a lengthy test proving they are capable of performing the job. It is entirely separate from a business license, for which anyone can apply and be approved. Most of these occupations are responsible for the well-being of people (doctors, teachers, and therapists), or for protecting the rights of people (lawyers, land surveyors), or handle materials that could cause harm (cosmetologists, contractors, electricians). Dogs are not people, but people are liable for them, and they can cause damage, which is why one would think the professionals in which people hire to train their dogs would need to be licensed.