Despite that, NASA has not been able to build a replacement for the Space Shuttle, leaving the USA at the mercy of Russia for reaching the International Space Station. This is largely a story of Congressional interference, which has forced NASA to waste money on building the horrendously expensive SLS rocket and Orion spacecraft despite there being no mission for them, while real missions and good science (and funding for simply buying launch capacity and crew services from American commercial firms) goes unfunded or gets cut.
The basic reason this happens is because Congress cares about NASA's inputs (money spend in their district, jobs created in their district, etc.) and doesn't care nearly as much about the results produced (tons of cargo delivered to orbit). A results-oriented approach can produce much more than NASA (which is producing zero, in terms of launch capacity) for much less money.
Prabhakar said it is essential for the Defense Department to reduce launch costs and increase launch frequency. “Where we are today is that it takes years to schedule a launch and billions of dollars to put anything of substance on orbit,” she said. “Huge shifts are going to be needed there, I believe.”Notice to the key terms - flight cost, and flight frequency. The SLS rocket that NASA is spending all its resources on is neither cheap nor expected to fly often. And the United Launch Alliance, the private-sector joint venture between Boeing and Lockheed Martin which has an effective monopoly on providing the military with space access thanks to its political pull in Washington D.C., is not a whole lot better. Why lower costs when there's no competition?
DARPA is part of the DoD, and ultimately the military does care about results. They want their satellites in place on schedule so they can carry out their military missions. It seems that their patience with the Congress-managed space programs at NASA and ULA is starting to wear thin.
Pictured Below: A DARPA rendering of a potential small-satellite launch system using a military jet as a first stage.