Some of what people basically want to know, or have heard they aught to know, the filter companies will tell you. Such as micron ratings.
Other basics are in the catalog. Such as anti-drain and some print their by-pass opening settings others don't but will tell you if you call.
Marketing is part of the equation.
However, as much as Winston thinks it's a shell game ..it isn't. There's always been, my media is better than yours.
There's always been choices for consumers from good, better, best.
However, OEM specs are the property of the OEM and not the filter company. It is not up to the filter company to publish them.
There has always been reverse engineering where filter company A doesn't know the VW spec for instance because they do not supply them as an OEM. So they utilize "standard" tests to test the OEM filter. Put it through the various testing equipment and come up with their equivalent that outperforms the OEM filter. That way they know they exceed the VW spec.
There are also, believe it or not, filter companies who are just aftermarket orientated ( some in Asia, middle east, south of the USA..) that would love nothing better than know for certain what the OEM spec is. OEM's know who the quality suppliers are.
Unfortunately, some want the absolute best performance filter to become the standard filter for OEM's. Those type of people whigne about the good filters that meet or exceed spec because they have determined for their use they want is the best and everyone should follow their choice.
What would you do if the OEM's clamped down on the better filters and started to claim they would void warranty because they are out of spec.
For now they aren't worried because the premium top of the line filter is less than 5% of the total market. If the OEM's wanted to get nasty, they could. But it is a low priority on their things to do. Designing new engines and the filters that go on them is more important.
It's not the OEM's that created the ..my filter is better marketing ploy..that was the filter companies to sell against the OEM spec filter. OEM's could tighten the specs so that all filters are the same..then what would you do..
So enjoy your ability to choose.