Most police departments use a risk matrix to decide whether to serve a warrant with a knock at the door by a uniformed officer or using a SWAT.
I know everyone hates to see a truck with armored steel on the sides and policemen wearing black helmets....but typically the SWAT is used when the individuals who live at the location have criminal history that includes credit vocation for violence involving weapons and or ownership if firearms.
That's certainly what was more likely the case some years ago. Interesting that you slip in the "and/or ownership if(sic) firearms" as a qualifier.
Times, they are a-changin':
"Dozens of federal agencies now have Special Weapons and Tactics (SWAT) teams to further an expanding definition of their missions. It’s not controversial that the Secret Service and the Bureau of Prisons have them.Department of Agriculture, the Railroad Retirement Board, the Tennessee Valley Authority, the Office of Personnel Management, the Consumer Product Safety Commission, and the U.S. Fish and Wildlife Service?"
Source: The United States of SWAT
http://www.nationalreview.com/article/376053/united-states-swat-john-fund