From "Law and Order" to "CSI," not to mention real life, investigators have used fingerprints as the gold standard for linking criminals to a crime. But if a perpetrator leaves prints from different fingers in two different crime scenes, these scenes are very difficult to link, and the trace can go cold.
https://www.motherjones.com/politics/2023/12/how-the-junk-science-of-hair-analysis-keeps-people-behind-bars/
Basically, hair doesn’t have enough unique characteristics to identify a person and your hair changes all the time depending on diet, age, sun exposure, etc. Lots of shit we use is unreliable: blood-spatter patterns, arson analysis, bite-mark comparisons, and now finger prints!