physics basically--same reason why wings aren't built with high rigidity (or with bricks).
brick walls have good downward (and in-line lateral) force resistance and suck at every other direction and torsion. tornado forces are multi-directional. wood frame walls are strapped down to the foundation in earthquake/tornado zones. plywood acts against (some) lateral and torsional forces.
plus, flying bricks are more dangerous to squishy humans.
Do you often have flying skyscrapers? Or pieces of concrete during tornadoes? Or even just rocks from mountains? The concrete technology is supposed to be able to achieve similar results. Does it take too much expensive concrete? What numerical comparisons are saying?
brick walls have good downward (and in-line lateral) force resistance and suck at every other direction and torsion. tornado forces are multi-directional. wood frame walls are strapped down to the foundation in earthquake/tornado zones. plywood acts against (some) lateral and torsional forces.
plus, flying bricks are more dangerous to squishy humans.