I think most doctors believe its beneficial but I also think they somehow see acetaminophen opiate formulations as some kind of bulwark against abuse.
That is, in large part, why it's in there. But, a lot of people are unaware of of acetaminophen's toxicity, and others will use it anyway, out of desperation, making it the "denatured alcohol" of drug prohibition. Instead of Jake leg, you get liver failure.
Myself, I won't take anything except aspirin when I want a simple over-the-counter pain reliever, and always insist on acetaminophen-free opiates.