"iTunes Extras aren't available in the Apple TV app on smart TVs and streaming devices."

"iTunes Extras aren't available in the Apple TV app on smart TVs and streaming devices."

Why NOT? Is it some contractual thing between Apple & the TV manufacturers?

Is there a work-around so that it IS possible? I'd like to be able to listen to directors' commentaries, etc. while watching a movie on a large screen. Thank you.