In Ready Player One, users that complete the second gate received a choice of a giant Robot:
Then something strange happened—something that had never happened when I’d beaten the original game. One of the “wise men” from the dungeon appeared on the screen, with a speech balloon that said, “Thank you. I am indebted to you. Please accept a giant robot as your reward.”
There were at most, two hundred robots:
A long row of robot icons appeared below the wise man, stretching across the screen horizontally. By moving the joystick left or right, I found that I was able to scroll through a selection of over a hundred different “giant robots.” When one of these robots was highlighted, a detailed list of its stats and weaponry appeared on the screen beside it.
Once a robot is taken, it cannot be taken by anyone else:
Eleven of these icons were grayed out and had a red “X” over them, and these robots could not be identified or selected. I knew they must be the ones taken by Sorrento and the other Sixers who had cleared this gate before me.
There are well over a thousand sixers,
If I had come here in person, my avatar would be surrounded by thousands of Sixers and I’d be at your mercy.
The Sixers are swarming all over Ludus. Thousands of them.
The Sixers had a huge head start on the Crystal Key
As the night went on, the Sixers continued to acquire copies of the Crystal Key.
Considering all that, why didn't the Sixers empty the robot dispenser? It would have been very easy for them, especially since
“The Sixers are using hacked immersion rigs,” I said. “Sorrento was boasting about it to me. They’ve got it set up so that different users can control the actions of every one of their avatars. So they can just have their best Joust players take control of each Sixer avatar during the match against Acererak. One after the other.”
The Robot is basically what helped Wade Watts win. Why didn't the Sixers empty the dispenser? It's almost like they wanted to lose.
And there's no way that the Sixers didn't know that the robots were one-per-person, as the second Sixer would have seen immediately that the first one's choice became greyed out.