We spread the news because this is what God has been doing ever since Genesis 12, for His Glory. He promised something to Abraham. Genesis 12:1-3 says, The LORD had said to Abraham, "Leave your country, your people and your father's household and go to the land I will show you. I will make you into a great nation and I will bless you; I will make your name great, and you will be a blessing. I will bless those who bless you, and whoever curses you I will curse; all peoples on earth will be blessed through you.“
Take note that the previous chapter, Genesis 11 is the story of the tower of Babel, which is created by man "so that they may make a name for ourselves and not be scattered over the face of the whole earth" (Genesis 11:4). As you may notice, what's at stake here is God's name, His glory, so he did what man feared most, to be scattered over the face of the whole earth by confusing their language.
Let's go back to His promise to Abraham, that He would bless him and that he would be a blessing to all people or nations on earth. You would notice that God's promise to Abraham is two-fold, that Abraham would be blessed, and that he would be a blessing to the whole world. Right after God confused man's language and scattered them over all the earth, He already had a plan of blessing them already. Isn't that amazing? Anyway, so we know why God promised to bless Abraham, so that he may also bless everyone else. Anyway, God is so serious about this promise to Abraham that he repeated it to Abraham's child, Isaac, and to the child of his child ,Jacob. (See Gen 26:4 and Gen 28:14) This only shows how God is passionate about His promise - To not only bless Abraham, but to bless all nations on earth. In fact, when you study the Bible, from Genesis 12 to the last book of the old testament, It is the fulfillment of God's first promise. In another fact, It was during this time that Israel was in its peak especially during the rule of David and Solomon, when the whole world looked up to the country of Israel.
Wait, how about the second promise? God did fulfill that too, and the first few book of the New Testament talks about it.
Galatians 3:16 says, "The promises were spoken to Abraham and to his seed. The Scripture does not say "and to seeds," meaning many people, but "and to your seed," meaning one person, who is Christ." Need I say more? Christ is the fulfillment of the second promise, He is the ultimate blessing, because through him, salvation was made available to mankind. The favorite verse, John 3:16, says, "For God so loved the world that He gave His only begotten Son that whosoever believes in Him shall not perish but have eternal life." That alone, should be enough for a real Christian, no more "Lord give me this" or "Lord give me that" prayers.
Christ not only secured salvation, but also, He prepared his disciples to preach the news to all the nations. (Matthew 28:18-20) "Then Jesus came to them and said, "All authority in heaven and on earth has been given to me. Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age." He did this because one cannot believe something without knowing it, John 3:16 says "That whoever believes".
Jesus did not forget the original plan of the Father, he trained a group of people to pass on the blessings to all the nations, so that God's promise would be fulfilled.
You see how God is passionate in pursuing the nations. In fact, he even set the end of age according to the nations. Matthew 24:3-14 is the conversation of Jesus and his disciples, who on that time wanted to know when the second coming would be. It says,
"As Jesus was sitting on the Mount of Olives, the disciples came to him privately. "Tell us," they said, "when will this happen, and what will be the sign of your coming and of the end of the age?“ Jesus answered: "Watch out that no one deceives you. For many will come in my name, claiming, 'I am the Christ, ' and will deceive many. You will hear of wars and rumors of wars, but see to it that you are not alarmed. Such things must happen, but the end is still to come. Nation will rise against nation, and kingdom against kingdom. There will be famines and earthquakes in various places. All these are the beginning of birth pains. "Then you will be handed over to be persecuted and put to death, and you will be hated by all nations because of me. At that time many will turn away from the faith and will betray and hate each other, and many false prophets will appear and deceive many people. Because of the increase of wickedness, the love of most will grow cold, but he who stands firm to the end will be saved. And this gospel of the kingdom will be preached in the whole world as a testimony to all nations, and then the end will come. "
There are still ALOT of nations which are unreached by this gospel, 2012 is a far-flung guess.
In Revelations, God gave us a glimpse why he wanted to reach all the nations.
Revelations 7:9-10 says, "After this I looked and there before me was a great multitude that no one could count, from every nation, tribe, people and language, standing before the throne and in front of the Lamb. They were wearing white robes and were holding palm branches in their hands. And they cried out in a loud voice: "Salvation belongs to our God, who sits on the throne, and to the Lamb."
It said that each nation was represented. That's what he wanted.