It's been shown many times that people will pick up random USB devices from anywhere and plug them into any computer without thinking. Airgapping just stops the automated scans and stuff that was already being stopped. Defence is reactive, so the momentum and advantage is always on the attacker side, and stopping the lazy ones doesn't do anything to stop the real threats.

People die in car crashes although they have seat belts, it's been shown many times, so seat belts doesn't do anything to stop the real danger.

The costs of seatbelts are already built in to the car. The cost of airgapping is not. The sheer inconvenience and limiting of the potential employee pool would put it far out of budget for anyone but governments or very large corporations doing very sensitive work, and even in those cases it would be on a site-by-site basis, not org-wide.

> The cost of ... far out of budget ...

Yes maybe, but now you changed the topic and started talking about money and how expensive things are. Have a nice day anyway

Viruses that infect USB devices can compromise systems based on air gaps.

Cf. eg., https://www.schneier.com/blog/archives/2013/10/air_gaps.html and https://www.schneier.com/blog/archives/2020/05/ramsey_malwar...