Well, you are describing the maximally absurd end of that spectrum to make your point, but in the US the FDA does indeed ban all kinds of stuff to prevent both its sale, and use (i.e. to stop "the stupid" from using it).

Blood glucose monitors are sold without a prescription in many countries, and you can buy them with varying degrees of accuracy and use them for whatever you want; not in the US, though, because they are regulated as medical devices.

The same is true for lots of other stuff that could be used in non-medical or less-dangerous medical contexts, like nebulizers.

You can make a reasonable argument for your position, regarding this specific device or more generally. But the FDA has consistently rejected it.