The rewards need to be re thought out.
After the season ends, the high point people should NOT receive the best box , and the lowest points people should NOT receive the lowest box. The high points people receive their name in lights and receive the coveted trophy. WHY WOULD YOU HANDY CAP THE PEOPLE WHO ARE NEW TO THE GAME?
You must switch the rewards. Give the high score the least amount of free boxes and the lowest score the most boxes.
In most of the competitive games, players that reach the top places receive better rewards than the ones on lower ranks. This gives players motivation to play and climb the ranks. Otherwise, they could easily stay on lower ranks and never climb up.