#1 OFFLINE "COLD" STORAGE
With almost a dozen crypto exchanges hacked and customers losing over $10B+ in BTC value, a hardware wallet is one of the greatest defenses. Your private keys are always stored offline meaning your coins are also always stored offline. As your private keys are never exposed to your computer or the internet, it greatly reduces the chance of a hacker, whether remote or local, being able to steal your coins.
#2 DATA ENCRYPTION
Most hardware wallets are fully encrypted with a PIN number and/or other form of authentication. This adds an additional layer of security. This way even if a hacker found your wallet, they will not be able to extract the private keys/seed phrases unless they also know your PIN.
#3 PC VIRUS PROTECTION
As private keys are stored on the hardware wallet, malware will not be able to find them like perhaps they could using a software wallet. Therefore, a hardware is immune to any computer viruses you may inadvertently download. In addition to that, most cryptocurrency wallets run their own operating systems so malware meant for Windows will do nothing against the operating system of the crypto wallet.
#4 VERIFY TRANSACTIONS
The latest hardware wallets requires you to confirm a transaction on your device (not the app on your computer) before any coins can be spent. This adds yet an extra layer of protection from any phishing hack.