They are not vulnerable, unknowing beings floating around waiting to be taken advantage of. They require respect and often humility to bring them through conjuration and they choose whether or not to come to you. Your reciting a conjuration opens the gate for any spirit(s) who want to come forward to do so to you specifically. Think about the words being a key turning the lock on a door and when you're done the door opens to the spiritual or astral realms. You cannot do a spiritual drive-by and scoop up unsuspecting spirits.  Spirits demand respect, rightly so, and you have to give respect to get it in anything in life including work with spirits