It is certainly not because of any earthly status.
A common symbol used in classical Christian art is the laurel wreath or crown. In the ancient world the crown signified many things, and Christianity adopted it when depicting holy men and women.
In the Greco-Roman world the crown was seen as a sign of nobility or social rank. It was reserved for those of significant status in society. Additionally, it was customarily given to the victors at the Olympic games as well as to victorious military commanders.
In this context the crown was seen as a symbol of high status and victory.
Christianity quickly adapted this image for its own purposes and its symbolic meaning can be found in several places in the New Testament.
For example Saint Paul writes, “An athlete is not crowned unless he competes according to the rules" (2 Timothy 2:4-6). Later on in the same letter he continues the analogy, “I have fought the good fight, I have finished the race, I have kept the faith. Henceforth there is laid up for me the crown of righteousness, which the Lord, the righteous judge, will award to me on that Day, and not only to me but also to all who have loved his appearing" (2 Timothy 4:7-9).
In the book of James we see this further highlighted, “Blessed is the man who endures trial, for when he has stood the test he will receive the crown of life which God has promised to those who love him" (James 1:12).
The image is repeated in a few other places in the New Testament and is reprised in the Book of Revelation where we read, “Round the throne were twenty-four thrones, and seated on the thrones were twenty-four elders, clad in white garments, with golden crowns upon their heads" (Revelation 4:4).
Based on these passages saints are those who rightly deserve a crown in art, representing their privileged status as residents of heaven and symbolizing their reward for “fighting the good fight" and “finishing the race." This is especially the case with martyrs, who endured such great suffering on earth.
Saints have endured trials, gone through incredible suffering, passing the test to be with the One whom their heart desires. They have traded the crown of thorns for a beautiful crown of glory.