That's it. You should have guessed that it's not government mandated when you reckoned that you have seen it in 90%, rather than 100%, of the pornos you've seen.
I've seen a different disclaimer before a Digital Playground movie that admitted something to the effect that some of the sexual acts depicted may not necessarily be 100% healthy or safe. I think that movie might have had some ass-to-mouth action, as well as being condom-free (like most porn today). I don't watch digital playground often enough to know if that's on all of their DVDs, or just some. But I think the disclaimer amounted to a "Don't try this at home, unless you already know what you're doing."

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