My dad worked for NASA during that time. The above is 100% what he said. NASA needed the air forces support which meant being able to launch large spy satellites. Which also meant the thing was really expensive making it a white elephant. It drained a the money that could have been spent to implement more modern launch systems. People used to get pissed off when I'd say the best thing for NASA to do was to stop flying the shuttle. Retrospectively that was the right thing to do.