It is not like these guys are carrying the devices in their hands and not doing their job. They are mounted units.

What is the first thing an investigator asks you when they get there? What did you see when you pulled up?

A Police officer at a departmental accident. Was the light green? What happened? Who was at fault?

These could all be answered by video. Gee I wonder why most police cars have videos hard wired into their dashboards?