Buying it from a doubtful source is the mistake they do in that case. Get it from the real source and you won't have such a problem. If you bought ledger nano from "some guy" then you could lose all that you have, but if you buy it from ledger directly and not from some random stranger, the problem drops a lot smaller.
Bought a hardware wallet from the third party or unofficial store is similar like asking a stranger to create a web wallet for you where he's already know your seed phrase and private key, it just his choice to rob your coins or not. Hardware wallet is the most safest storage because it's almost prevent from any malicious virus and keylogger which can steal your coins. People are careless for not buy a hardware wallet when they have a huge amount of money on their web wallet or exchange.
For the resellers, there must be an indication or like a seal, same on what we have on the product that we bought from the store to ensure that the item is still safe to use and have not been used yet by the reseller themselves. Hardware wallets is said to have a better security than the online wallets, I think that is because they are offline but I think there is still a threat once you connect them to the computer if you want to do a transaction or if you want to update the wallet.
We can also lost them or they can get damage over time. This can be the reason why some people don't bother on availing one anymore. Plus they still haven't experience any problem on using an online wallet.