The searches are for food and drink. They don't want anyone failing to pay their big markup on concessions.
That isn't cynicism talking, BTW. It's a Philly tradition to bring hoagies to an Eagles game. When the Eagles got their new stadium, the practice was banned. They tried to claim it was a homeland security measure, but the truth leaked out and the fans went ape-scat. (IIRC, the NFL was partly behind it; they get their cut, too.)
WOW! I can see why the fans got up in arms! Big time!