It is part of the ceremony here reqired by Law in the U.K
Someone may think it is funny to perhaps leap up, and then go "Only kidding!" but the problem is that by Law the cermony must then stop, the accusation be investigated, and the ceremony can only go ahead after the law Officers are happy for it so to do, which in practical terms will be on another day.
Bang goes all the Reception, the First Night and maybe the Honeymoon !
Any friviolous objection will at the very least attract a charge of Wasting Police Time, and maybe you will be sued by the Brides family, and may be punched by the Groom's !
Don't do it unless you really mean it !!!!