Revered Parris is motivated by an impulse to protect himself and his position in Salem. He calls for Reverend Hale in the hopes that Hale can authoritatively state that Betty Parris is not guilty of any social transgressions, but has instead fallen under the influence of witchcraft, witches, or spirits.
Parris discusses his concerns for the security of his position in Salem in the opening scene of the play when he and Abigail worry over Betty and the town's reaction to her illness. The town has also heard rumors of what the girls were doing in the woods before Betty became ill.
Parris is concerned that he will be forced out of Salem if Betty is accused publicly of dancing naked in the woods at night. This concern drives him to call Hale and to support the witch trials.
The trials serve to distance Betty from suspicion and from undesirable attention, thereby helping to maintain the security of his position in Salem.