If you get caught with a kilo of coke in your car, your car gets taken. They view it as a tool used in the commission of a crime. Kind of like confiscating a screw driver from a burglar. The money from these guys was taken because they had no way of justifying it. That said, they coukd argue since its a gambling case, it was used as a tool to further the enterprise; i.e pay winners and shylock.
If they have you on a wiretap discussing how you just bought a house with proceeds from a gambling operation, they will seize it. If you are meeting people in your home to sell drugs or take bets, you are using your home to further the commission of a crime. Trust me, i was on the wrong end of a this back in the day so i know first hand. I dont condone it but i understand it philosophically.