Funny, I noticed an absence of a far more cynical explanation that made me immediately doubt how balanced the article was: if cops know that the footage is difficult to obtain or can be easily suppressed, deleted, or otherwise buried, or if the legal system is already heavily biased in favour of law enforcement such that body cam footage rarely changes trial outcomes, then body cams don't actually contribute to additional accountability and therefore there's no reason to change behaviours.

tl;dr I see no reason to believe body cams have actually resulted in greater transparency or accountability due to offsetting institutional factors.