Speaking from first hand experience I can tell you it would take a lot more than start-up culture to change the way the software is built for the government. For one, a lot of agencies are regulated by DHS or DoD on what is allowed, prohibited, and open for discussion. Another big, and I'd argue bigger issue, is that many of the people in positions to make these decision are nearing retirement and for them it is advantageous to award lucrative contracts to those companies that are likely to employ them or their friends later.