In one of my Seminary courses, I responded to a rhetorical question. I'd like to share my response:

...since the fall of man, why hasn't mankind as a whole realized this and come back to our creator to be restored as His children?

Maybe our 'answer' can be found as we look upon our own previous lives of sin before believing in Jesus Christ. In our sinful condition, most of us had little knowledge of God and an even smaller desire to live 'right.' We weren't trying to look for God...only the next fleshly pleasure (whether it was money, sex, drugs, alcohol, etc). But God loved the world so much that HE gave...His love was commuted to us (Gentiles) through Jesus Christ. God reached out to the whole world...

Even as the world seems to delve deeper into sin, the harvest field is ripe. Through Jesus Christ, the way of restoration has been solidified, but the Way isn't plainly known to those in darkness - remember where we were. That's why it's important for us to go out into the harvest fields, do good works, and reveal a loving Father that desires His children to return home.

John 3:16-21 (KJV) - For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. For God sent not his Son into the world to condemn the world; but that the world through him might be saved. He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God. And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil. For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved. But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God.

Each of us carries a responsibility to share Jesus Christ in word and deed. It's not just for ministers, elders, pastors, and preachers (etc.). Every person that calls Jesus as their Lord and Savior must raise their banner. Regardless of the position or call to serve or plant or water precious seeds, we must trust God to grow a bountiful harvest in His time. Let us not become weary in well doing. Let us continue to serve our Father with our whole hearts. There's someone in darkness right now...