Why? The Love of Christ!
So why do we use our skills, knowledge, and resources to help those who can't pay us back? Because "The love of Christ compels us" (2 Cor 5:14). It is in response to His amazing love for us that we desire to love others as he loved us. We are merely sharing what he has already given us.
The passage continues, "that those who live should no longer live for themselves, but for Him who died for them and rose again" (2 Cor 5:15) Through Jesus death on the cross and His resurrection we can have forgiveness of sins and the promise of eternal life. All we need to do is trust in him, and let him transform us. Part of that transformation is living for Him, and that means loving others as He loves us.
If you would like to share the love you have already received, get involved!