Besides, there's all sorts of ways to skirt laws and regulations, but just because you can buy it in a store doesn't prove it is legal. Hell, a person may unknowingly buy it because they think it is a "video signal cleaners", and never be aware that it removes the macrovision signal.
I remember when Radio Shack was being sued by some guy who was spied upon by someone who had bought or built some device with parts from Radio Shack (I don't recall details - it was a long time ago.) Radio Shack eventually won, showing that they legally sold many devices that could easily be used for illegal activities as well. This is the same reasoning that the peer networks have been using: They admit that there is illegal sharing of copyrighted material, but that is not the sole use of the peer networks, thus they should be allowed to exist. It's kinda like saying cars and guns should be illegal, because they are used in bank robberies. While this is true, these are not the intended or sole use or cars or guns, and getting rid of them would either be throwing the baby out with the bath water (cars), or really wouldn't diminish the number of bank robberies (most bank robberies are accomplished with notes and the threat of violence.)
Not to mention the fact that many foreign DVD players disable macrovision, or at least allow it to be done after-market, but I can assure you: when it was made know that the earlier, very expensive Sony players did this many moons ago, that was a BIG deal. It's just that, at this point, it's a little too widespread for the studios to effectively deal with. That's why they went so vigorously after the kid who broke the CSS protection code. He wanted to post it on the Internet as "free speech", but the studios said it went directly against the DCMA. In the end, it was already so widespread across the internet that the damage was done, and the courts decided to drop it.