We seek happiness; we seek to please God. These two things go hand in hand.
From our point-of-view: What can really give us peaceful delight? Only the friendship of God. And we know that to have that friendship, we must please Him, rather than displease Him. He is our almighty Father; we are not His equals, but His little children. The only peace, the only happiness I can really have comes with my confidence that the invisible God smiles on me, blesses me, takes pleasure in the fact that He has a child like me.
From His point-of-view: He needs nothing from us. His fatherhood has absolute strength and sovereignty. Human parents naturally rely on the love, affection, and reasonable obedience of their children—and become stricken if this love, affection, and obedience is not forthcoming.
But God has no needs like that. He has everything to give and nothing to lose. Out of His infinite goodness, He has made all creatures, that we might by our goodness give Him glory. What pleases Him? That we be happy—truly happy, peacefully happy, as His friends.
Okay. So: Why did Christ submit to baptism? Let’s try to understand it by considering the two “offices” which the Christ possesses.