“because there is no negative impact on false positive, only some wasted effort by police.”

This is incorrect. You don’t need to be “arrested” to be detained on a false positive hit, and being detained can ruin lives, missed work, missed family obligations, social stigma of having been a suspect. Also these systems do not have a way to correct false positives, so it’s likely to reoccur to the same individual multiple times which will have a real psychological impact. These systems have also shown to have higher false positive rate when looking at minority’s this creates a risk of further creating a cognitive bias among police.

Don’t forget being detained as a suspect could result in you being added to a list you can’t remove yourself from.