Dan Burke speaks on why we need silence during the Holy Sacrifice of the Mass:
We need silence “so that all may dispose themselves to carry out the sacred action in a devout and fitting manner.” Here we have the wisdom of the Church, as the Holy Spirit leads us to eschew all human priorities outside of God and to draw our hearts to the reality of this sacred encounter. The Mass finds its ultimate purpose in the condescension of God to meet with us and nourish us — and for us to respond in a manner worthy of this gift of all gifts.
It stands to reason that our behavior at Mass will be proportionally devout to the degree we believe this meeting of heaven an earth is actually happening. In contrast, those that see the Mass as a kind of religious social gathering — and harbor disbelief or lack proper instruction — will see no need for such formality, and will act accordingly.