I can't imagine it would be that high. To do this, you have to at least be capable of locating your wallet.dat or similar file for the software you are using, moving it to a USB drive, and opening it again from the USB drive when you want to use it. If you can do that, then even just looking at a Ledger or Trezor and realizing they have a screen and buttons should be enough for you to realize they are more than just a simple USB drive.

Still, although obviously not as good as a hardware wallet, storing a wallet file on a USB drive is marginally more secure than just using a straightforward software wallet, since your wallet file is not connected to the internet at all times.

They can't extract your private keys remotely (as far as we are aware for the major hardware wallets), but they can still attempt to push malicious transactions to your device in the hope you will sign them without checking. Hardware wallets are still only as good as the person using them.