Business licensing of this type has 3 different tiers, really. Let's talk about each one.
Government certification
Where it's needed to protect citizens, governments will directly certify people to certain jobs. A structural engineer or airline pilot will be government licensed.
It wouldn't surprise me if the government is not involved in travel agent certification.
NGO (non-profit) industry associations
Who decides if you're a lawyer? Not the government - the Bar Association. The National Fire Protection Association writes the North American electrical code.
When a responsible NGO is already in place and doing a good job, the government often defers the role to them. The NGO is at their discretion to make prudent decisions about who that is. They can then sign contracts with that person, and that contract binds the person to whichever reasonable thing it says.
Private company networks.
Some industry infrastructure is run by private companies. A travel agent needs SABRE, a lawyer needs Lexis-Nexis. The companies can give access to anyone they want, on contractual terms which they choose, consistent with their profit motive and health and happiness of their user base.
These companies would be most interested in you keeping your contractual agreement, so they'd be more interested in your credit score than your test score.
Hotels, airlines, and others within the travel industry can also grant discounts to anyone they please, on any contractual terms which they please. So they are free to "turn the knobs" on those agent perks - they could say "only travel agents who have made at least 100 bookings in the past year"... or not.
In short: if these NGOs and private companies want to permit "anyone" to register and qualify as a travel agent, they are free to do that.
A method to their madness?
I suspect the industry is well aware of the "abuse" and tolerate it because at the scale it's happening now, it's more a benefit than a nuisance. (that could change if it became too popular). The benefit is such people are actually some of the most experienced candidates to be an actual travel agent. So they are "seeding" future agent candidates for the cost of some perks.
It's hardly the strangest thing industries have done to recruit. Airlines cut the "number of flying hours" required to become a commercial pilot to a paltry number, degrading safety in the eyes of many.