That's not 100% true. A rifle can't be suppressed to the same noise level as a pistol caliber. .300 black, maybe. But only by changing ammo.For LEO, pcc/sub guns have largely been replaced by carbines except where PC concerns of evil black rifles prevail. The reason is simple. A carbine can do anything a PCC can, but the opposite is not true.
Law enforcement made the change for money. The Feds started giving away M4 carbines, and a free M4 will beat a $1500 dollar HK MP5 every time.