Think about the money being made off commission. AB takes 4% of every sale. Therefore, it takes merely 25 days to make as much money as would have been made stealing everything from the site at once. Even if only half of the coins sent to the site get spent (I doubt that) it takes just over a month to make what you can steal in one day. It is FAR more profitable to keep the market up and running in both the long and short term.
Am I wrong?
You're right. But if people get bored they get bored. Who wants to work for the rest of their lives?