Most the times it is to break balls and let them know(Mobsters) that the FBI knows they are using them for illegal gambling and they hope by scaring them they won't return to the racket. I also think its an attempt to try to get mobsters on anything and really don't actually care about the poker machines as much as getting an indictment. I'm not a fanboy of the mob or anything but it seems at times the FBI becomes somewhat desperate and trys to get the mobsters on anything and some key cases were Jackie D' Amico's case was called weak by the judge, Operation old bridge almost all the guys are out, Vincent Badalamenti only getting two years. It seems to me that they would't care about the machines at all if they weren't connected to the mob