Because PDs and their citizens can’t afford all that data storage.
Data storage is still cheap. I have run helmet cameras on my motorcycle for over a decade now and I find that I can fit an entire day of riding into 128gb.
You can get unlimited cloud storage for relatively cheap on a per-account basis, too. The tech exists and it’s not that expensive. Maybe stop spending money maintaining unneeded MRAPs gifted to them by the Feds and they’ll easily have the money for it.