Because God has not appointed us to any quality of wrath, but unto possession of salvation through Jesus Christ our Lord (1 Thessalonians 5:9).
The day of the Lord will not take the grace believer by surprise, for he does not face the wrath of God. Therefore, all those in the Church will not remain on earth during any part of the Tribulation period.
Our happy hope is the return of Christ to take us from this earth (Titus 2:13). Once the Church has been removed, the man of lawlessness will be permitted to rise, and the Tribulation will begin with the signing of the seven-year peace treaty with Israel (2 Thessalonians 2:3; Daniel 9:27).