They don't need to ... AFU is one of the best.
However if you're shopping around, don't ever use an authentication service that hides the ownership of the website. That's a BIG red flag.
Also make sure that the authenticators have retail or manufacturing experience with high end designer goods --- just saying "I've bought LV (or Chanel or whatever) for 5 year" ... does NOT make someone an authenticator.
Make sure to avoid authenticators that cannot provide any references that include past work history that is associated with the high end designer goods. For instance, if someone has been a paper goods sales representative for the last 10 years, but suddenly decides they are an expert, that's NOT sufficient to make them a trusted authenticator.
Also, I'd ask here and perhaps on other discussion boards and get suggestions from people who have used authenticators. If it's someone that no one has ever used or heard of, then avoid them.
I could go on, but I thought these would be good suggestions for anyone who is looking for an authenticator.
AFU being the best is a matter of opinion. Just because you work for a designer or manufacturing company doesn't make you an authenticator, it makes you a salesperson. Most don't have the training or expertise to authenticate.
BTW....none of what you said should be "required" for a website is on A4U. No ownership of website, no experience in retail or mfg, in fact they say their authenticators are 'just regular girls' with years of experience in buying and selling. A4U is no different than any other authentication site.