Because a false positive ruins lives? Is that not sufficient? This man’s arrest record is public and won’t disappear. Many employers won’t hire if you have an arrest record (regardless of conviction). His reputation is also permanently smeared. These records are permanently public and in fact some counties publish weekly arrest records on their websites and in newspapers (not that newspapers matter much anymore)
Someday this technology may be better and work more reliably. We’re not there yet. Right now it’s like the early days of voice recognition from the ‘90s.
Human error is preferable, even if it is more frequent than the alternative, when it comes to justice. The more human the better.
Humans can be held accountable.