To put the "Certified By" or "Meets XXX Specification" a couple of things have to happen. The main one being the transfer of $$ to the certifying company. Sometimes those fees can be in the Hundreds of Thousands of Dollars. Another thing is that the certifying company will want a copy of the formulation that you are submitting. Keep in mind that Amsoil is a small company in the world of oil companies. I'm fairly certain that they are one of the largest privately owned oil companies in the world, but only do a small percentage of the business that some of the publicly traded oil companies do. The amount of money it costs to have that seal of approval stamped on is not cost effective for the volume of business they do.
Amsoil works with the companies that sell them additives, such as Lubrizol, to buy additives that are proven within the industry, & then add them to superior base stock to produce Amsoil's products. The specs (what it takes to be ATF+4 certified by Chrysler) are public knowledge (or at least can be found within the industry) & Amsoil tests every batch against it's own high standard. If it does not pass it will not be bottled. Amsoil offers a warranty to back the claims they make. I guess it comes down to trusting their recommendation. I have been using the products long enough & have seen first hand the benefits, that it is no longer an issue for me.
Also, if Amsoil was making claims that they were unable to back up, you would see every "Big Oil" lawyer filing claims against them. The big oil lawyers love nothing more than showing the false claims of other oil companies. Like this example
. In that case, Royal Purple had made some claims based on 12 year old testing, and BP, (Castrol's parent company) hired an outside lab to see if the claims were valid or not with the current RP products. Turns out Royal Purple pulled several of it's ads. These kinds of little lawsuits go back and forth on a regular basis & Amsoil has not been on the losing end of one, that I know of.
Amsoil has had double digit growth for the last 20+ years, even while other oil companies are losing market share & selling out. Amsoil's founder, A.J. Amatuzio, was/is a life long military man & was first exposed to synthetic oils in jet aircraft engines. At that time, in the '60s, he was curious as to why a product that performed well in the harsh conditions of the jet turbine, had not been used to make similar performance gains in the automotive industry. This became his new passion. By 1972 he had gained API approval on a 100% synthetic automotive oil. It was a 10W-40 (known as AMZOIL at that time), and was the FIRST synthetic to gain the API's approval. Now, nearly 38 years later, every major oil company has a synthetic product on the market with many of those offering "Extended Drain Intervals". A term that Mr. Amatuzio came up with to describe the ability of his "long life oil" to last longer than 3000 miles. He was mocked & it was was very hard to sell an oil that was in some cases nearly 3 to 4 times the price of the oil that was sold at the local service station at the time. He at that time built his company around the Word of Mouth advertising & marketing method we know today as MLM. For this product, Al Amatuzio felt that is was easier to explain the features & benefits of the product on a person to person level, thus his individual dealer network was started & remains intact.
I typed all of this to say this, Amsoil has been in business for nearly 40 years, Alan Amatuzio, A.J.'s son is now the "head Brewmeister" in the company. Most of the formulaitions are treated just like the Bush's Baked Bean recipes, meaning only 3 or so people actually know the formulation, and 2 of those people are named Amatuzio! They have have lead the way in synthetic technology and are not limited by a board of directors wanting to see a profit margin. All oil companies have the opportunity to produce products of this caliber, however most will not due to the cost of goods.
As long as "Big Oil" has a marketplace full of consumers that are willing to dump their oil & replace it at 3000 miles, no matter the true condition of the oil or the environmental consequences, why would they change? However, many OEMs are changing their recommendations to drain intervals of 7500 miles or more and oil companies are losing market share to synthetics like Amsoil & other specialty oil companies. Castrol introduced the EDGE product and advertises 15,000 miles, M1 has the Extended Performance line also a 15k product.
Amsoil has a great history of leading the synthetic industry and the products are some of the best available. As long as you are working with a qualified dealer and using the products as Amsoil intended you will have no problems while using them.
Here is a video that covers the history of Amsoil, for those who may be interested.