The Space Shuttle wasn’t just the NASA follow up to Apollo – oh no, it was intended to replace all expendable launch vehicles, both those in use by NASA for civilian payloads and military launches. The specifications of the payload bay and the overall design of the shuttle were driven by military payload requirements, namely for a particular spy satellite that the Hubble Space Telescope was based off of.
For polar orbital missions, the Shuttle was to use SLC-6 at Vandenburg Air Force Base as its launch site. The Shuttle never made any launches from California, however, as plans for military use beyond what missions had already been conducted and scheduled were dropped after the Challenger Disaster.
SLC-6, originally planned for the Gemini based Manned Orbiting Laboratory program and later remodeled for the Shuttle, would eventually launched Delta IV boosters for the Military. The Air Force would continue to develop Delta, Atlas, and Titan boosters into the 2000’s and beyond, leading to today’s current Atlas V and Delta IV Boosters.
The Shuttle would launch a few more military payloads, but none into polar orbits. The deciding element on much of the Shuttle’s design, it’s military usability, wound up barely playing a factor in it’s operational life and actual flight history.
It’s also worth noting how this short video mentions the cost savings associated with the reusable STS program, something that, as we all know now, was not to be.