Genesis 2:18

And the LORD God said, It is not good that the man should be alone; I will make him an help meet for him.

God, Who is the believer's heavenly Father, cares for His children.  He looked down into the garden and saw that His creation was all alone, and, like any good father, He had pity for the man.  His concern for the man sprang Him into action to remedy the situation.

God had already created plenty of living beings.  There were animals on the earth and animals in the ocean.  There were birds that flew in the air.  However, none of those beings were equal to the man.  None had the man's intelligence.  None had his dominion.  None were suitable to be a "help meet" for him. This goes to prove that God knows what is best for man.  God made man to be a societal creature, so he would need someone with whom he could carry on conversation, give and receive information, and give and receive affection.  God knew that the pair would be better than the individual (Ecclesiastes 4:9) because each could lend their support to the other.  Matthew Henry states in his commentary on this verse: "Perfect solitude would turn a paradise into a desert, and a palace into a dungeon."  As much as some introverts like to be alone from time to time, no one likes to be alone ALL the time! God simply did not create us to be alone.  

God made a helper to cohabit with him.  In this union, God also provided the means to replenish the earth.  No man can procreate without the help of a woman, and no woman can procreate without the assistance of a man.  God made them to come together in a "one flesh" union (Genesis 2:24) for life. God knew what He was doing.

Society rejects this notion in this era, but that makes it no less the truth of God's Word.  God made man and then He made woman.  He paired them together for His glory and their good. It is what it is, and no matter how much we buck against it, it will remain the way that God designed it.