What is the attack scenario you feel a hardware token protects you against that a software token will not (for the use cases U2F was designed for)? Sure, hardware tokens prevent malware from actually lifting your private keys. But, to steal your software private keys you likely need malicious code running on your computer. And, once an attacker has that, it is largely game over for all intents and purposes anyway. They can ask your hardware token to sign bogus requests, steal your passwords, etc. Sure, with a hardware token you can wipe your machine and feel semi-confident that you get to keep your private keys. But, really, once your machine has been compromised and you wipe it, setting up new private keys sounds like a wise practice regardless. I'm not arguing that hardware tokens have zero use. But, for most users, the attack model where hardware tokens shine is likely not of value to them.