Have we forgotten that when we purchase things from out of state we still have to pay taxes on them? It's just that the seller doesn't have to collect that tax

Have we forgotten that when we purchase things from out of state we still have to pay taxes on them? It's just that the seller doesn't have to collect that tax for our state when they don't have a physical presence here, but that doesn't get us off the hook. Now, I understand that no one really pays the tax, and that most states will let you pay a flat fee to cover any taxes you might have owed (if they are under a certain amount), but rest assured that if you make a massive (think car, boat, or artwork) out of state purchase, they will be looking for that tax money.