So the "gun show loophole" is not a fallacy?
It's only a fallacy if you don't get caught.
ATF and local le are always around trolling at gunshows, and if they catch you- or the seller - they bust you.
If you really want a firearm, and are not allowed to own one, then just buy a black powder revolver - with cash. They're not subject to the same regulations as modern firearms.
"Why aren't they?"
No one does a drive by with a cowboy gun.