You don't get the same resources, respect, or pension of the military. If you are let go/fired, you have little chance of finding something comparable close by.
It's not healthy for the psyche to be put into harm's way for an entire career span. There is probably a lot of untreated PTSD going on. It's not surprising that they are very leery of policies that would put them or fellow officers at risk, or be guinea pigs for policies pushed down from above.
People get awkward or remain guarded around police in social settings, so law enforcement tends to fraternize with each other and their families.
None of this makes for an environment that promotes transparency.
I'm not making any judgements for or against any of the events that have transpired. But I have sympathy for everyone involved. I suspect that the police-public dynamic will never be changed without a significant cultural shift in attitudes.