But to remain in the flesh is more necessary on your account. (ESV)
When you think about it, if it is so grand for us to be with Christ, why do we spend any time on this Earth at all? We know that it would be better for us. We would have no sickness, no sorrow, no pain, no depression, no poverty, no hatred, no killing, no deception, no sinning of any kind! Why stay here?
Paul says, remaining in the flesh is more necessary. Why? On the account of the church. Paul had planted the Church in Philippi. He continues on in helping them to grow in their faith and carry out the work of proclaiming the Gospel. Yes, he could go to heaven. But, God has willed him to remain on the Earth for the benefit of assisting the Church.
The fact is, we all have a purpose on this Earth. And sadly many Christians do not realize what that purpose is. We are Christ's ambassadors. We are called to carry out the message of God's grace to all the world around us. That is why we are here. That is why God has not called us home to be with him just yet. If you are reading this right now, your purpose is to be an ambassador for Christ.
We will have all of eternity to enjoy the blessings of the Savior with no distractions from the enemy of our souls. In the meantime, we have a wonderful purpose. We are part of God's wonderful plan to bring as many souls with us to Heaven. That purpose is far greater than your current career, greater than how your 401K Retirement Plan is doing, and how your sports team is playing.
2 Corinthians 5:18–20
 All this is from God, who through Christ reconciled us to himself and gave us the ministry of reconciliation;  that is, in Christ God was reconciling the world to himself, not counting their trespasses against them, and entrusting to us the message of reconciliation.  Therefore, we are ambassadors for Christ, God making his appeal through us. We implore you on behalf of Christ, be reconciled to God. (ESV)