Serial killers, by definition, have multiple victims. Bundy had 20, Gacy had over 30, and Ridgeway had over 40. To make a movie focused solely on their victims lives wouldn't be possible in even a three hour movie. For Bundy that would be about 12 minutes per victim. A lot of people are fascinated by serial killers, mainly to try and understand what and why they did it.

Serial killers are glamorized in the media and I don't necessarily agree with that. At the same time, everything in movies is glamorized, thats what they do to sell seats. Theaters don't exactly play movies that are documentaries. There are some things to check out if you are interested in more of the victims backround. I think the Morbid podcast does a good job on giving detailed backgrounds on victims leading up to their demise.