I’ve driven a lot in urban places with speed camera programs (which I fully support along with other car reduction and traffic calming designs) and lots of pedestrians and cyclists around, but I’ve never had a camera ticket in 20 years of driving.
Eight years ago I was driving on a genuinely empty back road in a rural part of America, speed limit 55mph. I failed to notice that, for one mile, the speed limit went down to 45mph. The character of the road didn’t change, we weren’t passing through a populated area. I don’t know why it changed. For miles in either direction it was 55. I kept going 55 and put absolutely zero people at risk of anything. That oversight cost me $400, and the cop was a huge asshole about it. So I bought a radar detector.
There are various layers of dysfunction at play in American road design and policing that I’d happily advocate we address. In the meantime I’m doing what I can to avoid any interactions with power drunk people who have the ability to decide my fate on a whim.
The assume-good-faith answer to a speed limit dip like that is usually that the road has one or more intersections with some risk factor. Like limited visibility around a bend or hill, or a short merging/acceleration area, or prone to flooding in rain, or intersection with a bike trail. Of course, any particular spot like yours could be a police cash grab, but there are many places where something like that seems arbitrary but there is a real reason. Best to follow the signs, for conditions you might not know about.