I am guessing political reasons. The Police chief and Mayor would have to justify the police officers using their weapons to the news media and the public.
Probably in rural areas the citizens and the police have a much better relationship. The citizens have respect for and trust the police, and expect them to be armed well enough to do whatever they might be called on to do, and assume that they are intelligent and well trained and will do the right thing.
I would guess in the bigger cities you have more of the welfare state anti-police mentality, plus the people and the lawyers looking to hit the legal lottery in a lawsuit against the police.
I am sure the lawyers and the families of the thugs would be screaming that the police are mowing down "disadvantaged urban youth" - or however they would be defending the thugs as - and it had to finally get pretty bad to be able to allow the street cops to have a patrol rifle available to them in order to give them a chance against the thugs armed with AK-47s.
In Palm Beach County, if the sheriff’s deputy qualifies with an AR, he can have it. He has to buy his own, unless he gets on one of the tac teams. In many of the towns around here, the same policy applies. If the officer chooses to take the rifle training and purchase the rifle, he can have it. Quite a few of them do so.
I think the Broward County Sheriffs Department also allows its deputies to carry a rifle in the car after they qualify, but again, they have to buy it. I’ll have to check. I see mostly Palm Beach, only a few Broward deputies.
I’ve also been told some very disturbing things about this shooting by police officers in Palm Beach County. I’ll see a friend of mine tommorrow and try to verify some of it.