Well, I guess Hertz's rationale is that you most likely made 2 reservations by accident... It's a bit hard for one person to drive out with 3 cars at the same time since technically you would be the only authorized driver (unless you added an additional driver)...

If you went back to cancel the reservations, why did you make 3 reservations in the first place? Better yet, why would you be upset that Hertz cancelled 2 of the 3 reservations when you don't seem to have the intention to pick all 3 up?