I honestly think that the reason that pushers got sidelined was safety.  I read a magazine that was stating that the first planes (mostly pushers) had a tendancy of killing pilots cause when the plane crashed, the engine would break loose and crush the pilot.  Once the engines were mounted up front, that problem went away.  Since then, most all planes have been built around the tractor prop.  I personally think that if that original problem didnt exist, we would see alot more aircraft with pushers.