There are people who relish victimising others.
Getting their ‘victim’ overpay a water bill or redo something already properly done, gives them pleasure.
Yes, Exploiters have mental issues, often provoked by being unwanted all their lives.
Getting a chance to exert their will over others grants them a pleasure they rarely know.
Where a normal person has others who care about him/her, the Exploiter has no one.
Sure, they buy a companion and pretend, but they know that no one loves them, or ever will, no one wants them, or ever will, and in their anger they lash out, trying to exploit everyone around them that they can.
This, of course only makes them more hated.