Because using it commercially means making money off government resources.

Needs to be a change so that government-funded stuff is free to use for non-commercial purposes, but anyone using it for commercial purposes has to pay a licensing fee.

One case a few years back, a TV station filed a DMCA takedown notice against another site that had posted footage that was frame-by-frame identical to a clip on one of their news broadcasts. The “pirated” footage? Footage from the Mars rover. The site they filed the takedown notice against? NASA.