For us the purpose is to have fun. As the AM my purposes extend to training. By using the FA to coordinate and encourage team play I find we do better on the tournament and Spire. Mostly because the FA encourages people to get to know each other, interact, chat, and communicate about things. I also am using it to train people in the fine art of leadership....not an easy thing when you have so little "control" over the players. So, in the long run, in my opinion, the "prizes" aren't as valuable as the experience in team building. This has been shown in my case to be particularly good as I've noticed a lot more cohesion in the team as we continue to progress up the ranking in the FA and in the game. "Success breeds success," as they say.
AJ