When the Lord needed someone to warn Judah to turn from their evil ways Isaiah volunteered--he wasn't drafted nor was he forced to. We know God doesn't force anyone to obey Him. But, seeing the need he chose to prophesy and preach the Word of God to his nation.
There are many places, near and far, where the Word of God has still not been preached. Not long ago a brother who preaches in Toronto listed all the major cities in Canada where there is not a sound church. The same kind of list could be made of churches in the northern part of the States. There are entire countries like Paraguay, Uraguay, and Guyana in South America where to our knowledge there is not a Gospel preacher. And the list goes on and on.
Where are the Isaiah's of today, who are willing to carry the Word of God, not only to places far, but also near? We live in a county of 65,000 people where there are 52 (count them) churches of Christ, yet we still find people who are looking for truth and obey it. No matter how many Christians there are in an area there are still more people who are seeking the truth. Will you volunteer to take the Word of God to them?