[openasocket]

I imagine it's a part of a trend of "militarization" of law enforcement. In the last few years police forces have greatly expanded their SWAT forces, partly because of the practice of the US military giving away surplus military tech to law enforcement. And if you have a hammer, all the world seems like a nail.

The rationalization is that serving warrants can sometimes be risky, so why take the chance? It's in law enforcement's best interest to err on the side of caution: better to scare the crap out of people than get shot without warning. Which is why the government and the courts are supposed to balance LE's concerns with the rights of the people.