Young people can be criminals too. And if the police catch them while still juvenile, they might have more of a chance to turn their life around.
Young people can also go missing, and facial recognition of security cams could help find them.
I honestly can't see any reason why children shouldn't be included like everyone else.
It goes without saying that a conviction should never depend on computer matching, and that safeguards need to be in place to prevent abuse and limit to legitimate law-enforcement purposes.
But trying to locate suspects or victims in the first place? Children are no less important here than adults.