Some people do it out of arrogance because in their minds no rule of any kind should ever apply to them and I dont think they realize that it notates gold and mvp on boarding passes so they think nobody will know. Others do it out of jealousy and envy that they arent in First class or asked to board early. I recall one individual say in a loud tough guy voice "Look at those first classers standing around waiting to rush on the plane to sit there and wait for me to get on...it aint leaving without me" Needless to say this tough guy so forgot his words and mobbed the gate as soon as boarding began. After all why should someone be allowed to board early who spends 5 figures on airfare a year