Government agencies are made up of people. Those people develop relationships with their providers, when they like them. They've been around long enough to have seen good providers and bad providers. When they find a good one, they hang on to them for a while.
Eventually someone above them shakes things up a little, and a new provider upsets the incumbent and takes over the work. After a few tries - or the first if they're lucky - they'll find another good provider, and the cycle starts over.
That's why bidding on a job isn't where the opportunity is won. You almost always win or lose the job before the solicitation is released. You win by building relationships with the people that make up these agencies. Do research, set up meetings, go talk to people, figure out what gives them heartburn, and develop a solution to their problems.
That solution becomes the framework for the new solicitation. You have then influenced the requirements. And congratulations, the bid has now been tailored to favor your company. You will probably win!