This article struck a chord with this statement:
By requiring Acrobat the government gives preference to a particular software vendor, assuring that thousands of people who otherwise would not choose to use Adobe software are forced to install it. Worse, endorsing a proprietary, narrowly supported technology for government data poses the risk that public information could become inaccessible if the vendor decides to stop supporting the software.
Emphasis mine. These are very real problems. Government software vendors are required to go through extensive checks. Has Adobe? Has the USG inadvertently created a vendor relationship by selecting a proprietary technology as the sole way to interact with the government, regardless of if the USG is paying that vendor to use its software?