Perry Mason: El caso del asesino a sueldo

For me, all Perry Mason episodes follow exactly the same pattern; presentation of the murder, the wrong person arrested, some red herrings, and the final voilà the solution with the clues and reasoning that Mason must have been tying up together the previous night after nobody knowing when he got the sources. Always, the conjuring trick. My question here is: why did the scriptwriters or the producers take off the Amy Hastings character, Ken Malansky's fiancée??? It was the only pair of people that imbued some life into any of Mason's stories. And the only who were not wooden-like when together.