Why 110m hurdles for men and not 100m?
Because the hurdles for men are set at different distances from
the starting line than for women. For example: The mens hurdles
start at the blue line, so the womens would start about 2 inches
away at the yellow line.
Additionally, elite men's stride length would not allow them to
hurdle at the distance that womens hurdles are set at; it's simply
too short.