The reason I do it is simply to feel accomplished. I don't do it for bragging rights or for the cool looking emblems. If that were the case, I would have stayed at 8th prestige which was my favorite. However, knowing there were two more prestiges to go, I felt like there was a hole I needed to fill. So, I do it because I want feel like I completed that part of the game. Now I'm 10th, or master, and I feel like a huge weight has been lifted. And that's the reason I prestige.