@freemo I'm not denying the simplicity. But you have to draw the line somewhere, and this is a reasonable place to draw it. You can't stop people from buying gasoline or styrofoam, but you can make it illegal to combine them or sell branded napalm.
As for the poisons, "no restrictions" is nonsense. You're definitely going to get your ID checked when you buy poison, just like you do when you buy a lighter. It's not the full background check, but there will be *some* check that at least you're an adult, and it probably stores that ID swipe in some databank somewhere for future investigators.