Light bars, cameras, comms equipment. The traffic enforcement cars need those. Not so much the armor and detainment capabilities.

If it’s known they don’t pursue and aren’t likely to attack you to secure an arrest, the risk for them from the person they’re stopping (traffic on the e.g. highway they’re standing next to is another matter) in an encounter is a ton lower. Why fight them when you can just leave? And rack up another charge, sure, but one a hell of a lot less serious than attacking someone and then still fleeing.

It does mean calling in a regular cop for arrests, but what proportion of stops result in arrests in a day? They also have to call in tow trucks and ambulances and fire trucks.