Only the Trinity can satisfy the Christian longing to give Jesus Christ unreserved, unabashed, direct worship. “… that everyone will honor the Son, just as they honor the Father.” (John 5:23)
“How many Gods do you worship?” One.
“Do you worship the Son?” Yes.
“Are the Father and the Son one God, or two Gods?” One.
Revelation 5 is blasphemy if the Father and the Son are not the same being. It is joy if God is Triune — three distinct, inseparable persons, and one being, one essence, one God.
Also, only the Trinity can satisfy the human longing to relationally know an ultimate being who is intrinsically relational. If God is only one person, his relationships begin, not continue, with creation. If God is three persons, then creation is the spill-over of intra-Trinitarian relational joy, and our joy is to enter into this fellowship of the Father loving the Son, and the Son loving the Father.