Credential mills flourish because few people take the time to understand how the numerous and varied credentials from a state driver’s license, school diploma, and whatever title, such as CPR certification, are legally and ethically bestowed upon individuals. Many people willingly accept the provider’s assurance that the credential being offered through some processes of training and qualification e.g. testing is valid.
Credential mills flourish, too, because of constraints of time and money. Any ten minutes, day, night, or whenever, and $20 dollars spent online for CPR certification easily trumps the cost for a live instructor and scheduled time, normally hours out of the business day, for actual classroom learning and CPR qualification.