alt Hacker NewsOne answer is that ALPRs have much too high an error rate (John Oliver claims it exceeds 30%) to rely on them for dragnet surveillance.
Maybe it makes sense to track specific vehicles, with safeguards such as warrants and also checking make/model/color, but it makes less sense to just give the government a 30-day rolling database of the public's movements in total, especially when 30% of those data points are inaccurate and thus not useful as evidence.
I don't know where this stat comes from. It doesn't square with our experience of Flock cameras. There is a truly high error rate in the underlying hotlist data the state maintains and the cameras rely on. But, like, cameras randomly flagging the wrong car, I don't think we saw that happen even once.