Jessica loves to be amused and entertained by her slaves. So while shocking this slaves cock is amusing on its own, it will amuse her more if he serenades her while she him. So she will have him perform various tasks for her while she electrocutes his cock like naming all fifty states and singing her a lullaby. It may look ridiculous for him but it pleases Jessica which in the end is all that really matters. And its not like she is only being cruel, she does let him adore her calf while she electrocutes him.