The Lords supper refers to the death and resurrection of Christ so why would we have 2 sacraments to symbolize the same thing.
Everything refers to the Life, death and resurrection of Christ. You could also include His ascension.
That you refer to them as symbols may be the reason for your doubt and confusion. They are not symbols. They are salvic events. One in entrance into the Kingdom, the other Communion, is life sustaning within the Body of Christ. It really does not matter if one is only baptised and you fail to maintain that new beginning by partaking of communion. See John 6:51ff.
