A hardware wallet allows you to spend coins without exposing the private keys. To spend e.g. a paper wallet, you have to swipe the keys on a computer. Yes, that can be offline, but a HW wallet reduces the amount of possible mistakes in this process.
[1] https://en.bitcoin.it/wiki/Hardware_wallet#TREZOR_The_Bitcoi... [2] https://doc.satoshilabs.com/trezor-faq/threats.html#what-hap...
If you want to be really secure you can engrave your recovery seed into a piece of metal that won't melt in typical house fire temps like brass.