Why does communion have to be blessed by an ordained pastor in the Baptist Church?

This is simply a tradition for this faith. Someone decided to do it from the begining of their religion.

This is not simply tradition. The Bible speaks of God setting apart some for teaching, some for preaching and other roles. The clergy are set apart for Word and sacrament. This is a fulfilling of the scripture and is to be emphasized as different from a love feast. Love feast are meals by Christians.