Laws that give the police _less_ power are generally written in blood. Meaning, there has to be a pattern of clear and obvious abuse for any change to happen. For instance, the now near-ubiqitous police body cams are a result of multiple well-publicized unprovoked beatings and murders.

The reason for this is that no politician is going to willingly step up for more police oversight and restricted powers, for at least a couple of reasons:

1) They will be painted by their opponents as "weak on crime" or even "supporting criminals" at election time.

2) They risk losing votes from emergency services workers, which are quite a large demographic in local elections.