Because people may destroy the CCTV, but the fingerprints of each person is not the same when we fingerprint people commit crimes, will make it possible to catch the bad guy.
Because the criminals may destroy it, but the integrated camera, fingerprint, but it's not the same when we have the fingerprints of the crimes will be able to catch criminals.
Because the criminal may destroy the surveillance cameras, but the fingerprints of, but it is not the same when we design the fingers crime to catch the culprit.