That's fine if you don't want to do anything after you log in, but in that case you may as well have just logged in with your npub instead.

Nostr requires your private key to sign for EVERYTHING you do, not just logging in.

React to someone's post? Bust out your hardware wallet so you can sign for that.

Zap a hilarious meme? You'll need your hardware wallet again.

Reply to a GM post? Yep, you'll need your hardware wallet for that, too.

You don't just log in with your private key and then you are good to go until you log out. Every action is an event that must be cryptographically signed for the protocol to consider it valid, so you would be having to sign with your hardware wallet the entire time you were using your Nostr client.