It is not because He needs them!
(Charles Spurgeon, "A Good Start!")
"God is not served by human hands, as if He needed anything — because He Himself gives all men life and breath and everything else!" Acts 17:25
Let no man imagine that God needs any of us. He was perfect — perfectly happy and perfectly glorious — long before wing of angel moved in space, or time even existed! God ever was and still is self-contained and all-sufficient. If He chooses to make any creatures, or to preserve or use any of the creatures He has formed — it is not because He needs them, or is in the least degree dependent upon them.
"Surely the nations are like a drop in a bucket; they are regarded as dust on the scales; He weighs the islands as though they were fine dust. Lebanon is not sufficient for altar fires, nor its animals enough for burnt offerings. Before Him all the nations are as nothing; they are regarded by Him as worthless and less than nothing. To whom, then, will you compare God? What image will you compare Him to?" Isaiah 40:15-18
"Do you not know? Have you not heard? Has it not been told you from the beginning? Have you not understood since the earth was founded? He sits enthroned above the circle of the earth, and its people are like grasshoppers. He stretches out the heavens like a canopy, and spreads them out like a tent to live in. He brings princes to naught, and reduces the rulers of this world to nothing!" Isaiah 40:21-23
"I have no need of a bull from your stall or of goats from your pens, for every animal of the forest is Mine, and the cattle on a thousand hills! I know every bird in the mountains, and the creatures of the field are Mine! If I were hungry I would not tell you, for the world is Mine, and all that is in it!" Psalm 50:9-12
"Who has ever given to God, that God should repay Him? For from Him and through Him and to Him are all things. To Him be the glory forever! Amen." Romans 11:35-36