it’s a simple use it or lose it situation. SWAT teams cost money, and they always have to justify their existence. If they sit around the coffee pot waiting for the one or two incidents a month (or maybe even fewer) when their skills are needed, the next budget won’t have any money for their shiny toys. So they’re out serving no-knock warrants, and 7 year olds get killed. It’s basically the same thing that happened at Waco.
Bottom line: if you give law enforcement officers military equipment and training, don’t be surprised when they start acting like a military force.
It’s interesting how SWAT just kept developing and holding out the hand for more money. Every community with twenty thousand folks...has a SWAT capability. In most rural counties...the Sheriff and his deputies will claim a SWAT capability even if it’s not totally true.