They really don't. You are interning at a small part of a small agency.
Even 2 agencies qualifies as "more than one would think" with the federal government. I suspect there are more than just NASA and NIH.
The federal government uses more macs than one would think. I'm an intern at the National Institutes of Health right now - and almost every computer I run across is either an iMac or Mac pro. The few Windows machines that are in use (for Windows only applications) are Lenovos.
Won't be the case if Apple stops being compliant with EPEAT!