standing for the choson

Question

It has become common for most (perhaps the uninformed) in attendance to stand when the choson and kalah enter and walk down the aisle to the chupah is there any basis for this minhag (perhaps it is from the practice to stand at a wedding ceremony in a church)? I was once told the reason for this is “choson domeh l’melech” if this is the case why not stand for him all year? Why stand for the kalah? I heard a story of a Chasidic rebbe who after washing for bread at a shevah brochos discovered there was no salt on the table, he took his bread and tapped it on the sholder of the choson saying “choson domeh l’melech (melach)”! I was told this is the extent of “choson domeh l’melech” today.