>Absolutely is not. Most intelligence departments, Department of justice, homeland etc all have some departments with air gapped machines for security reasons.

This is actually not true except in some edge cases. Most of the "air gapped" networks are actually only logically separated. For example DOD's NIPR (often referred to as the "low side") is their version of what most companies have, the network most directly connected to the internet, as well as the DREN (for research and development). No classified data is allowed here.

But they also have other networks, sometimes referred to as the "high side" (i.e. SIPR, JWICS), where classified data (Secret and Top Secret, respectively) can be stored. It's a common misconception that these are air gapped, but they're actually more like a VPN on top of NIPR. Additionally, there are various "gateways" (i.e. DOTS, Cross Domain Enterprise Email Service) to allow limited communication and data transfer between low and high sides.