I mean, the US had programs for that too. See the X-20 Dyna-Soar.

The genius of using the shuttle as a bomber is stealth. Not regular steath, but hiding in plain sight.

The USSR were worried the airforce could launch a shuttle with a nuclear bomb into an orbit near Moscow (or other targets), but claim it was just a regular launch with a regular payload with totally legitimate reasons for that orbit. Actually, with the shuttle's cross range ablities the orbit could be several hundred kilometers off the target.

And it would look like a regular flight as it climed into orbit and spend 20-30min floating towards Russia. Soviet command wouldn't be able to identify it as a threat until 3.5min before impact.