Interesting question ... With many possibilities ... For example in western culture it was or is traditional for the groom to carry the new bride into the house ... But how many have asked why is a tradition.... Relax I'm going to spill the beans :) In Rome it was considered really bad luck if the bride tripped when entering her new house for the first time, so to avoid this the groom would carry her over the threshold to avoid any tripping ... So apart from cultural traditions there are also deep and generally unknown psyscological drives at work ...