Why do vibrators say not to use on unexplained calf pain??

You're correct. Since anything that vibrates could be used as a general body massager, they don't want people thinking they have sore tight calves, using the vibrator on them, and then causing the clot to break free and reach the lungs or heart resulting in death. It's a rare chance and I'm sure the cases of a vibrator being involved in a blood clot death are insanely few and far between, but it's a CYA move on the manufacturers' parts to protect them from the liability, should this incident arise.

And as you'll find with most warnings of this type, the warning is there now because at some point, somewhere, it happened to someone. Same reason there's a warning on your hair dryer not to use it in the shower - they're not simply assuming people are stupid, but at some point someone tried this, died, and whoever made the blow dryer was held liable for NOT telling them not to do it. Notice all the 'hot' warnings on the fast food coffee cups since that lawsuit in the 90s?

Again, this is only a guess on my part, but orgasms can induce labor so I'm guessing that the manufacturers are trying to protect themselves against lawsuits from pregnant women that went into labor prematurely after having an orgasm using a vibrator.

There's actually a thread on this somewhere. They are safe for MOST women in MOST pregnancies but in high risk pregnancies, specifically ones carrying a risk for preterm labor, some doctors and professionals will recommend against it because the contractions from the orgasm could possibly trigger labor contractions. It all depends on the specific doctor and the specific pregnancy as to whether or not it's deemed 'safe', but based on all of my research, it's only a problem for abnormal or risky situations.

There's also a conditional called placenta previa, wherein penetration by a rigid toy or even PIV sex can trigger placenta bleeding and possibly terminate the pregnancy or harm the fetus. But that still fits into the high risk pregnancy category.

So it's basically (besides placenta previa) more of a concern about the orgasm itself and not the vibrations? I guess that makes more sense.

I can second that... as much as I tried to orgasm my way to labor my little man was STILL 6 days late. Lol

I knew there had to be some sort of medical reason for all that, and that is really interesting. Death by vibrator. What a way to go out huh?

Now I know I can massage my cramped legs then, because I don't have any blood clots Thanks guys!