> a police officer could easily sit in a fixed location and take down license plate numbers that pass by

Not on a busy road. And not while identifying the faces of the drivers.

Nor the dents and identifying marks, effectively. Nor within a realistic budget (24/7 * average officer hourly rate * # of Flocks nationwide + time spent sharing with desired other jurisdictions + cost to analyze).

Point driven in by fellow commenters this year: scale matters!