They are used to keep money in the tournament area. If you were to play in a single table satellite for lets say $125 with 10 people. $1250- the $10 per person dealer fee = $1150. But when you win or get down to heads up and decide to chop it they only give you 2-$500 buy in chips and $150 cash (cash to tip dealer). Now you could use that to play in the $1030 single table which if you win is enough to buy into the main event.

You can use them to play another $125 stt and 3 of the other players at the table could just give you their $125 cash = $500 buy in chip thats how you could get cash back. Or if you win the $10000 they will give you 20-$500 buy in chips which you could sell to a player paying cash into the main event. More than likely the player buying in for cash will try to ask for a discount on buying your chips. I was fortunate enough to have someone give me the 10k without trying to beat me down a dime. So essentially once players moneys go into the tournament area it is hard to get it back out of the tournament area. They can be used for other tournament buyins also, not just the main event.