Because this is the after-death destination of people who Now escape personal judgment. This was opened up to the Gentiles because the Nation of Israel (Jehovah's wife-like people) rejected "the Lord of Glory". Once the Bride of Christ is filled, others who escape judgment will live on earth.
Paul was the "Apostle to the Nations" (Gentiles) so he wrote a lot about their destiny. But it's still all about escaping judgment. There is no need what-so-ever for anyone to end up at the Great White Throne Judgment where their eternal condition is on the line.