If you buy a second hand hardware wallet that was NOT tampered with, it is usually possible to just wipe it and generate a new seed phrase. If you'd do this, you'd be safe.
But the thing is that nearly everyone do not know if a hardware wallet is tempered with or not. Many people do not know the difference between original and fake hardware wallet. They can see the fake as cheap and that can encourage them to buy one instead of buying one directly from the official site or from an official reseller.