The Psalmist says, "Enter his gates with thanksgiving, and his courts with praise!" Then he adds, "Give thanks to him; bless his name!" Our worship is not an exercise in mere thankfulness. It is a practice of honoring our Redeemer and Lord. It is a matter of blessing Yahweh. It is a matter of coming in to God's presence.
God is everywhere. But he has promised specifically to be present where two or three are gathered in his name. He is delighted to receive us when we come. When we show up, we hear him gladly say, "Come on in!"