Still people are use private keys or mnemonic words? Why dont you use encrypted file? By using an encrypted file + password you are much more protected against spy attacks.
I personally view this as the act of laziness on the part of the wallet owners or much more, they aren't aware of the danger in exposing one private keys. Many wallets had been hacked due to the owners negligence of their passphrase, password and their private keys. Practically, hardwallet still remain the best form to keep your coins or valuable tokens safe.
Also, I will like to say cold wallet could.be best too if the holders can use the computer in storing their tokens or coins. The problem with cold wallet is if the computer network port can be remove from the computer system. I have been using this type of cold wallet for my coins and tokens, and never encounter any challenge of any sort.