You never know how soon or how many iterations until after the goal has been achieved. Sometimes something like the smartphone explodes relatively quickly after

You never know how soon or how many iterations until after the goal has been achieved. Sometimes something like the smartphone explodes relatively quickly after the concept starts coming together. Other times you're waiting decades upon decades to turn the corner, like with fusion power. Humanoid robots have fallen into the latter category for too long for most people to jump at each advancement being "the one" anymore. Afterwards, everyone will agree it was obvious ${ADVANCEMENT} was really the one which would do it - but not before.