Why has God left believers here on earth after saving them?
God has left believers on earth to be a testimony and to carry a burden for lost people. They are to constantly remind the lost that salvation is not by what they do or what they think they can become, but by faith—believing and appropriating what God has provided in Christ.
Les explains that after God imputes Christ's righteousness to a believer by faith, it does not stop there. Believers will get busy, be a testimony, and have a concern for lost people. He notes that nothing thrills him more than a new convert suddenly being overwhelmed with the lost condition of their family, loved ones, neighbors, or coworkers. That is as God intended. That is why He has left us here: so we can constantly remind lost people that it is not what they do or what they think they can become; it is what they do in the area of faith—do you believe it? Have you appropriated it?