You'll find that the major manufacturers often adopt a "we have no comment on the issue of headphone break-in." I can see why.
If manufacturers make some kind of statement on break-in, consumers will react in different ways.
"I didn't notice any break-in effects. What's wrong with my headphones?" Due to the fact that the consumers either didn't notice break-in, or the phenomenon doesn't exist, some may feel let down that they didn't notice an improvement in sound.
If a headphone manufacturer makes a promise, however subtle, it may lead to disappointment or confusion. That's why they stay away from making comments; it opens a big can of worms.
If the sound really gets better, this would be an obvious choice for manufacturers, as headphone business is a lot about performance and about how they perform sonically against competition (with regard to e.g. cables, the story is quite different). Burn in doesn't cost much, it does not require any overseeing, and if headphones are constantly produced - there would be no 'lag' because of burn-in in production. And I agree - unfortunately, the world is not run by scientists - that's why we have so much BS here and everywhere
What I had in mind was a recommendation in a manual that your headphones will sound better after burn-in. This doesn't cost anything at all Does Sennheiser, AKG, Grado or any other manufacturer put such recommendation in their manuals? If not, why are they hiding such an important secret from you???? Or maybe they all are ignorant?