We can trace the woman as reward trope all the way back the beginning of the medium itself as [...] upon successful completion of many arcade games players were rewarded with a related smooch of victory trope, so named for the kiss the hero received as a reward for rescuing a kidnapped princess. Sometimes the prize is blatant as with the standard hero reward in which the king will give his daughter to the hero. On other occasions it's taken a step further by employing the parallel of sex for victory or rescue sex trope.