They have Tommy guns, they just don’t use them on the street anymore.
Per local tradition, Agents here get to shoot the Tommy gun as part of their last firearms qualification day before retiring. Otherwise their main function is public relations during the range day for the FBI’s Citizens Academy program.
Back in '86 we got to shoot the Thompson, the MP5 and M16 on our last qualification day at the academy.
The first indication a bad guy should have that I'm dangerous is when his
disembodied soul is looking down at his own corpse wondering what happened.