Generally speaking the vendors in attendance won't allow you to hold or handle animals they know are prone to biting unless you are very serious about buying it despite the temperament. Even vendors I've seen with good sized black throat monitors would prefer to hold it themselves while you inspect it even if they know it to be fairly docile. Species that are more naturally flighty/bitey usually aren't held by buyers at all and are inspected through a deli cup. No one wants their babies rampaging through an expo, right?