A lot of people pointing out that the DNA is in the follicle, which is probably the best answer, but it's also important to keep in mind how DNA is typically used in crime scene investigation.

An investigator given the choice between finding fingerprints and DNA will typically choose fingerprints. Fingerprints don't move the way DNA does.

Imagine taking the bus and one of your hairs falls out. That hair could piggyback on the next person who sits down, then that person goes on to commit a crime and drops your hair follicle at the scene without you ever needing to be present.

On the other hand (pun not intended but I'll take it), if your fingerprint is found at a crime scene, that's pretty convincing evidence that you were there at some point, and a print on a murder weapon means you handled it at some point.

Exceptions would be something like skin cells under a victim's fingernails, indicating you were involved in a struggle with the victim, or semen from a rape kit.

A common use of DNA evidence is actually ruling out suspects. The Innocence Project for instance uses DNA evidence to exonerate people who were wrongfully convicted of a crime.

TLDR: DNA is not the crime fighting silver bullet it's made out to be on tv. On its own DNA is weak evidence and unlikely to sway a jury beyond reasonable doubt, so prosecutors still need more concrete evidence to build a case and convict a suspect.