Faceted aerospace planes

I note that designers came up with faceted aerodynamics for aerospace
plane designs during the I950's-1960's- there are Kraft Ehricke's
Convair Shuttlecraft: http://www.astronautix.com/craft/concraft.htm
.... and the Soviet M-48/VKA-23 design:
http://www.astronautix.com/craft/vkasign1.htm for instance, then they
seem to fall out of favor, only to return during the 1980's in some of
the transatmospheric vehicle designs:
http://www.abo.fi/~mlindroo/SpaceLVs/Slides/sld057.htm What exactly was
the faceted approach about? Was it to simplify the computation of
shockwave interaction during hypersonic flight? Allow for controllable
expansion of the vehicle's outer skin without buckling from differential
heating during reentry? Or in the case of the 1980's designs; stealth-
such as was used in the F-117?

Pat