Tyranny of riches. We have SWAT teams in nearly every police department around the country. Even our local regional department with 14 officers have SWAT training and equipment and could easily get a judge to give them no knock warrant. When you have a hammer, you look for excuses to use it.
We should legislate the number of SWAT teams and keep them at a certain level(i.e. county, certain size city etc). There should be a very deliberate process for their use and that should include a risk assessment of collateral damage and a "return on investment" assessment. If we had fewer teams, we would never see them used for small drug dealers or other petty crimes, and we would see their effectiveness increase while their collateral damage would decrease.