I would imagine there is a system already made to immediately fit in the cargo bay of the shuttle similar to the patriot launcher, besides we have aircraft like the Aurora that can get up real close, the bottom line is we do not want to tip our hand with our best or latest technology. Save the good stuff for when we really really need it.
I doubt it but the more important factor here is what we are showing the world. The message is something like:
“Yeah China shot one down before us. We don’t care about doing that as a test. But when we WANT to shoot one down we simply use the same missiles that HALF OUR NAVY SHIPS CARRY AROUND ALL THE TIME. Hah! Suck on that chumps!”