Upper Surface Blowing (USB)

I recall that USB was mentioned in several books of the 1980's, not
simply for transport, but as a method of producing STOL close air
support and bombing aircraft.
While the russians had a transport, and I believe we also did, I
haven't seen much more about USB, and nothign about applying it to
tactical attack aircraft.
Is this just a case of it never happened because the money wasn't
there, or was there somethign in the concept that proved less aimiable
to general use than first thought?