I don't think that's a reason, they're not secret (the YouTube reconstructors I mentioned (legally) get them after all - there are public if paid archives) they're just not available on that system. Just like all kinds of other stuff isn't. I think it's simply niche interest. Plus it's only any good when you haven't taken off yet and are about to land, i.e. the times cabin crew will do what they can to have you not enjoy any kind of entertainment whatsoever anyway.
