The true motivation of why God saves is a mystery. By mystery, I do not imply that it is foreign or abstract theologically. By mystery, I am speaking of the fact that God's motivation to seek and save the lost is His Love. And since God is Love, we understand this Love dwells in unapproachable Light. It is the very infinite and inexhaustive heights, depths, lengths, and breadths of God Himself. Which obviously cannot be wholly grasped with the understanding. Yet, understood insofar as we know Him through the revelation of Christ Jesus ([b]John 17:3[/b]; [b]1 John 4:9[/b]; [b]2 Peter 1:8[/b]).
Now, to direct this towards your question.
What Reidhead said, I beleive he even yelled this out, was that man's votive and free will offering of love and thanksgiving and praise, or purpose, was to give God glory. I don't believe he specifically said this was why the Son of God became flesh and died upon a cross. The cross and the sufferings of Christ indeed purchased this very thing; that is, the affections of man's heart through the cleansing of His blood. We may very well say this, in part, is the glory of God revealed unto men -- that there is peace with God through the ministry and gospel of reconciliation.
But when he says, "I didn't send you out there for them, I sent you out there for me!" He is relating the desire of God that none should perish but [b]that all be reconciled unto Himself[/b] through Jesus Christ. Or to be specific, for the reward of His Son's obedience ("may the Lamb who was slain receive the rewards (we sinners) of His suffering!") -- and thus, to the glory of the Father.
So, God seeks and saves the lost both because of His abounding love and mercy and for His glory. As it is that both His Love and Glory are revealed in no greater way in this world than through the redemption of lost souls -- at least, that is until He returns again to redeem the just and the righteous.
Though I should mention that when I say that God saves men for His glory, I am not implying in any way that God is being selfish. And neither am I deflecting a double standard between God and sinful men; for it is God Himself who set the standard ([b]Luke 6:35[/b]). To reiterate, the glory of God, in part, is revealed unto man by the revelation that there is peace with God through the ministry and gospel of reconciliation, that is, the gospel of Jesus Christ.
[b][u]In example[/b][/u]
"[b]I didn't send you out there for them,[/b]" so that you could be a good humanist, or philanthropist, and ease the discomforts of a dying and godless generation.
"[b]I sent you out there for me![/b]" To declare My glory: I have sent My Son, Christ Jesus, into the world, not to condemn the world but that the world through Him might be saved unto everlasting life!
Remember when Reidhead was explaining that he "primarily" went to Africa because of his sympathy (seeing the pictures and hearing the sob stories) for the discomforts of the heathens; he said something to the affect, "I will go out there and preach Jesus so as to ease the heathen's sufferings in this world." Rather than going to Africa because of his love for Jesus, his Lord and Savior, Who died for those heathens and Who is lovingly seeking to manifest the glory of His salvation unto them.
And that's my story, I'm sticking to it! :-P