I'd also say that the funding philosophy has changed significantly. Things like the space program and DARPANET came from a time when the government sought to fund high-risk/high-reward programs - programs that were unlikely to succeed, but would have a significant impact if they did. Now the approach is much more conservative, we only fund things that appear to be fairly low-hanging fruit. When a small company demonstrates success, the follow-on work is usually scooped up by the large, beurocratic defense giants like Boeing or Northropp Grumman.