So we'll buy off craigs list (classifieds), black market, in Mexico, and so on. You can't regulate all sales, and if you try the end result is best described as "if you outlaw guns, only outlaw will have guns". Or scuba tanks, as the case may be.
The flip side is e.g. my dive computer's manual starts with a page on how I shouldn't be diving with it, or at all, stating essentially that the device is not fit for its stated purpose. If you take it literally.
I know my sarcasm doesn't come across well on here. I'm not advocating that things are regulated. I'm advocating that people should stop creating a level of hysteria over what is likely to be a crappy product. It's no more dangerous than conventional scuba equipment. It's just not as good.