Military supersonics just aren't that important. We don't have Mach 3+ planes anymore not because we forgot or some nonsense, but because the things we used them for we now use space for: Need to spy on someone? The USSR is less happy to shoot a satellite out of the sky (this will change soon) than Mr. Powers in a plane. Want to nuke someone in a few minutes? ICBMs are mature technology.

So what are they supposedly offering the military?